CN207819862U - A Broadband Amplifier with Adjustable Gain Powered by Single Supply - Google Patents

Abstract

The utility model discloses a kind of broad band amplifiers of the adjustable gain of single supply power supply, amplifying circuit, adjustable gain circuit, seven rank LC passive filter circuits and attenuator circuit are fixed including prime, the input terminal that prime fixes amplifying circuit connects input signal, prime fixes the input terminal of the output end connection adjustable gain circuit of amplifying circuit, the output end of adjustable gain circuit connects the input terminal of seven rank LC passive filter circuits, the input terminal of the output end connection attenuator circuit of seven rank LC passive filter circuits.It ensure that the flatness in 1M 40M passbands, realize the 3dB decaying of 1M and 40M；Prime fixed gain circuits of the OPA690 as entire amplifier, AD8367 realize adjustable gain, HMC470 is as radio frequency attenuator, to adjust the gain of entire circuit as intergrade.1MHz 40MHz bandwidth, 0 ~ 40dB adjustable gains can be achieved.The utility model select single supply power supply, wide bandwidth, low noise high performance chips, only the single working power of need+5V, can reduce the workload of Power Management Design in electronic system.

Description

A Broadband Amplifier with Adjustable Gain Powered by Single Supply

technical field

The utility model relates to a gain-adjustable broadband amplifier powered by a single power supply, which belongs to the technical field of electronic communication and information engineering.

Background technique

The main function of the amplifier is to amplify the voltage or power of the input signal, and it is mainly composed of a transistor, an integrated operational amplifier, and a power supply. It has a wide range of applications in instrumentation, communication, radar, automatic control, home appliances and other fields.

Bandwidth refers to the highest frequency at which an op amp circuit can give a specified output amplitude. An amplifying circuit whose ratio of the upper limit operating frequency to the lower limit operating frequency of the amplifier is greater than 1 is called a broadband amplifier. In addition to being widely used in microwave and communication fields, broadband amplifiers also play an important role in instrumentation. For general electronic instruments such as oscilloscopes and signal sources, as well as biomedical instruments, certain signals need to be conditioned and amplified. These signals have a wide frequency range, from DC signals to AC signals of tens of MHz. The bandwidth of ordinary operational amplifiers is often difficult to meet the requirements.

The gain of the amplifier refers to the ratio of the voltage amplitude or power of the output signal to the input signal. The size of the gain directly indicates the amplification capability of the amplifier. Common integrated op amps have a constant gain when the external resistance is constant. However, in instruments and meters, it is often necessary to adjust the gain according to the size of the input signal. When the input signal is small, the gain needs to be increased; when the input signal is large, the gain can be adjusted appropriately to stabilize the output signal. Therefore, the amplifier whose gain is adjustable in a wide range has important application value.

With the development of Internet of Things technology, there are more and more portable instruments. In the push-type instrument, batteries are often used for power supply. Batteries can only provide a single positive voltage. The amplifier circuit in the instrument is often powered by positive and negative dual power supplies, and usually requires a DC-DC power supply chip to convert the positive power supply into a negative power supply and then provide the amplifier with operating voltage. The conversion efficiency of DC-DC is generally not high, which affects the power consumption of the entire system.

Common gain-adjustable amplifiers are often powered by positive and negative dual power supplies, such as AD603, VCA821, VCA810 and other gain-adjustable amplifiers can only work in the case of positive and negative dual power supplies. Portable instruments such as automatic weather stations and automatic weather station signal simulators are mostly powered by batteries. Batteries can only provide positive power. Therefore, it is very necessary to design a wideband amplifier with single power supply and adjustable gain.

Utility model content

The technical problem to be solved by the utility model is to overcome the defects of the prior art and provide a gain-adjustable broadband amplifier powered by a single power supply.

In order to achieve the above object, the utility model provides a gain-adjustable broadband amplifier powered by a single power supply, which includes a fixed front-stage amplifier circuit, an adjustable gain circuit, a seventh-order LC passive filter circuit and an attenuation circuit. The input end of the amplifying circuit is connected to the input signal, the output end of the pre-stage fixed amplifying circuit is connected to the input end of the gain adjustable circuit, and the output end of the gain adjustable circuit is connected to the seventh-order LC passive filter circuit. The input end, the output end of the seventh-order LC passive filter circuit is connected to the input end of the attenuation circuit.

Preferably, the pre-stage fixed amplifier circuit includes a P1 interface, a P2 interface, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R7, a resistor R8, an OPA690 chip, a capacitor C1, and the -IN port of the OPA690 chip Connect the resistor R2 in series with the ground, and the +IN port of the OPA690 chip is grounded in series with the resistor R5, capacitor C1, and resistor R7 in sequence. The input signal is connected to the node between the capacitor C1 and the resistor R7 through the central node of the P2 interface, and the peripheral metal of the P2 interface is grounded. , the node between resistor R5 and capacitor C1 is connected in series with resistor R8 and grounded; the -Vs port of OPA690 chip is grounded, the +Vs port of OPA690 chip is connected to VCC, and the VOUT port of OPA690 chip is connected in series with resistor R1 to -IN port of OPA690 chip. The VOUT port of the OPA690 chip is connected in series with resistors R3, R4 and the central node of the P1 interface, and the peripheral metal of the P1 interface is grounded.

Preferably, the adjustable gain circuit includes a P6 interface, a resistor R18, a resistor R16, and an AD8367 chip. The INPT port of the AD8367 chip is connected to the central node of the P6 interface after the INPT port is connected in series with the resistor R16. The peripheral metal of the P6 interface is grounded, and the resistors R16, The nodes between the P6 interfaces are connected in series with the resistor R18 and grounded, and the P6 interface is connected to the P1 interface.

Preferably, the adjustable gain circuit includes a sliding resistor R10, an inductance coil L1, a P5 pin header, a capacitor C11, a capacitor C21, and a resistor R21. The GAIN port of the AD8367 chip is connected to the 2 ports of the P5 pin header, and the AD8367 chip The DETO port of the AD8367 chip is grounded after connecting the capacitor C11 in series with the capacitor C11, the DETO port of the AD8367 chip is connected in series with the capacitor C21, the two ICOM ports of the AD8367 chip are both grounded, and the 1 port of the P5 pin header is connected in series with the sliding resistor R10 , The resistor R21 is connected to VCC, and the sliding end of the sliding resistor R10 is grounded.

Preferably, the gain adjustable circuit includes resistor R11, capacitor C20, capacitor C18, capacitor C14, resistor R17, resistor R15, capacitor C19, resistor R19, capacitor C16, P4 pin header, resistor R13, resistor R14, capacitor C17, P7 pin row, capacitor C12, capacitor C13, capacitor CD1, inductance coil L2 and P3 pin row, the MODE port of the AD8367 chip is connected in series with the resistor R11 and resistor R13 to the VPSI port of the AD8367 chip, between the resistor R11 and the resistor R13 The node between the nodes is connected in series with the capacitor C14 to ground, the node between the resistor R11 and the resistor R13 is connected to VCC, the VPSI port of the AD8367 chip is connected to the ground after the capacitor C16 is connected in series, and the VPSO port of the AD8367 chip is connected in series with the resistor R14 to VCC. The VPSO port of the AD8367 chip is connected in series with capacitor C17 and then grounded; VCC is connected in series with capacitor C12 and then grounded. Capacitor C13 and capacitor CD1 are respectively connected in parallel at both ends of capacitor C12. Port 1 is connected to port 2 of the P3 pin header.

Preferably, the seventh-order LC passive filter circuit includes IN1 interface, OUT1 interface, resistor R31, capacitor Cap1, capacitor Cap2, capacitor Cap3, capacitor Cap4, capacitor C31, capacitor C36, capacitor C37, inductance coil L3, inductance coil L4 , inductance coil L5, inductance coil L6, inductance coil L7, inductance coil L8, inductance coil L9, resistor R32, the central node of the IN1 interface is connected in series with resistor R31, inductance coil L7, inductance coil L3, inductance coil L8, inductance coil L4, The inductance coil L9, the inductance coil L6, the central node of the OUT1 interface, the peripheral metal of the IN1 interface, and the peripheral metal of the OUT1 interface are grounded, the node between the inductance coil L6 and the central node of the OUT1 interface is connected in series with the capacitor Cap4 and grounded, and the resistor R32 is connected in parallel Both ends of capacitor Cap4, capacitor C31 are connected in parallel at both ends of inductance coil L7 and inductance coil L3, capacitor C36 is connected in parallel at both ends of inductance coil L8 and inductance coil L4, capacitor C37 is connected in parallel at both ends of inductance coil L9 and inductance coil L6, and inductance coil L8 The node between the inductance coil L3 and the inductance coil L3 is connected in series with the capacitor Cap2 and then grounded, the node between the inductance coil L9 and the inductance coil L4 is connected in series with the capacitor Cap3 and then grounded, and the P7 interface is connected to the IN1 interface.

Preferably, the attenuation circuit includes an IN2 interface, a capacitor C0, an HMC470 chip, a capacitor C9, a capacitor C8, and a capacitor C7. The central node of the IN2 interface is connected in series with the capacitor C0 to the RF1 port of the HMC470 chip. The peripheral metal of the IN2 interface is grounded, and the HMC470 The VDD port of the chip is connected to +5V, the VDD port of the HMC470 chip is connected in series with the capacitor C7 and grounded, the capacitor C8 and the capacitor C9 are respectively connected in parallel at both ends of the capacitor C7, and the OUT1 interface is connected to the IN2 interface.

Preferably, the attenuation circuit includes a P8 DIP switch, a pull-up resistor, a capacitor C36, a capacitor C37, a capacitor C34, and a capacitor C35, and the 2 ports, 4 ports, 6 ports, 8 ports and 10 ports of the P8 DIP switch are respectively Connect the left end of the pull-up resistor, the right end of the pull-up resistor is connected to +5V; the 10 port of the P8 DIP switch is connected to the V1 port of the HMC470 chip, the 8 port of the P8 DIP switch is connected to the V2 port of the HMC470 chip, and the P8 DIP switch The 6 ports of the P8 DIP switch are connected to the V3 port of the HMC470 chip, the 4 ports of the P8 DIP switch are connected to the V4 port of the HMC470 chip, the 2 ports of the P8 DIP switch are connected to the V5 port of the HMC470 chip, the NC port of the HMC470 chip is grounded; the AGC6 port of the HMC470 chip After the series capacitor C35 is grounded, the GND port of the HMC470 chip is grounded, the AGC5 port of the HMC470 chip is grounded after the series capacitor C34, the AGC4 port of the HMC470 chip is grounded after the series capacitor C37, the AGC3 port of the HMC470 chip is grounded after the series capacitor C36, and the AGC2 of the HMC470 chip Port, the AGC1 port of the HMC470 chip is connected to the AGC3 port of the HMC470 chip.

Preferably, the attenuation circuit includes a capacitor C6 and an OUT2 interface, and the RF2 port of the HMC470 chip is connected in series with the capacitor C6 and OUT2 and grounded.

Preferably, VCC is powered by +5V.

The beneficial effects achieved by the utility model:

The utility model uses high-speed operational amplifier OPA690, high-performance variable gain amplifier AD8367, and attenuator HMC470 as the main chips, which ensures the flatness in the 1M-40M passband and realizes the -3dB attenuation of 1M and 40M. Among them, OPA690 is used as the pre-stage fixed gain circuit of the entire amplifier, AD8367 is used as an intermediate stage to realize adjustable gain, and HMC470 is used as a radio frequency attenuator to adjust the gain of the entire circuit. All chips operate from a single supply. Can realize 1MHz-40MHz bandwidth, 0~40dB gain adjustable. Based on the design principles of single power supply, wide bandwidth and high gain, the utility model selects high-performance chips with single power supply, wide bandwidth and low noise, and only needs a single working power supply of +5V. The workload of medium power supply design avoids the problem of low efficiency when using DC-DC chips to obtain positive and negative power supplies. Anti-interference measures such as capacitive decoupling and filtering are comprehensively applied to reduce amplifier noise and suppress high-frequency self-excitation. The whole system has simple structure and superior performance.

Description of drawings

Fig. 1 is a block diagram of the utility model;

Fig. 2 is the circuit diagram of OPA690 fixed gain circuit among the utility model;

Fig. 3 is the circuit diagram of AD8367 gain adjustable circuit in the utility model;

Fig. 4 is the circuit diagram of 7 order LC passive band-pass filter circuits in the utility model;

Fig. 5 is the circuit diagram of HMC470 attenuator circuit in the utility model;

Fig. 6 is the magnitude-frequency response diagram in the utility model.

Detailed ways

The utility model will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the utility model more clearly, but not to limit the protection scope of the utility model.

A gain-adjustable broadband amplifier powered by a single power supply, comprising a pre-stage fixed amplifying circuit, a gain-adjustable circuit, a seventh-order LC passive filter circuit and an attenuation circuit, the input end of the pre-stage fixed amplifying circuit is connected to an input signal, The output end of the pre-stage fixed amplifier circuit is connected to the input end of the gain adjustable circuit, and the output end of the gain adjustable circuit is connected to the input end of the seventh-order LC passive filter circuit, and the seventh-order LC passive filter circuit is connected to the input end of the seventh-order LC passive filter circuit. The output end of the source filter circuit is connected to the input end of the attenuation circuit.

Further, the pre-stage fixed amplifier circuit includes a P1 interface, a P2 interface, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R7, a resistor R8, an OPA690 chip, a capacitor C1, and the -IN port of the OPA690 chip Connect the resistor R2 in series with the ground, and the +IN port of the OPA690 chip is grounded in series with the resistor R5, capacitor C1, and resistor R7 in sequence. The input signal is connected to the node between the capacitor C1 and the resistor R7 through the central node of the P2 interface, and the peripheral metal of the P2 interface is grounded. , the node between resistor R5 and capacitor C1 is connected in series with resistor R8 and then grounded; the -Vs port of OPA690 chip is grounded, the +Vs port of OPA690 chip is connected to VCC, and the VOUT port of OPA690 chip is connected in series with resistor R1 to the -IN port of OPA690 chip. The VOUT port of the OPA690 chip is connected in series with resistors R3, R4 and the central node of the P1 interface, and the peripheral metal of the P1 interface is grounded.

Resistor R1=resistor R2=402 ohms, resistor R3=100 ohms, resistor R4=0 ohms, resistor R5=0 ohms, resistor R7=59 ohms=resistor R8, capacitor C1=0.01uF.

Further, the adjustable gain circuit includes a P6 interface, a resistor R18, a resistor R16, and an AD8367 chip. The INPT port of the AD8367 chip is connected to the central node of the P6 interface after the INPT port is connected in series with the resistor R16. The peripheral metal of the P6 interface is grounded, and the resistors R16, The nodes between the P6 interfaces are connected in series with the resistor R18 and grounded, and the P6 interface is connected to the P1 interface.

Resistor R18=57.6 ohms, resistor R16=174 ohms.

Further, the gain adjustable circuit includes a sliding resistor R10, an inductance coil L1, a P5 pin header, a capacitor C11, a capacitor C21, and a resistor R21. The GAIN port of the AD8367 chip is connected to the 2 ports of the P5 pin header, and the AD8367 chip The DETO port of the AD8367 chip is grounded after connecting the capacitor C11 in series with the capacitor C11, the DETO port of the AD8367 chip is connected in series with the capacitor C21, the two ICOM ports of the AD8367 chip are both grounded, and the 1 port of the P5 pin header is connected in series with the sliding resistor R10 , The resistor R21 is connected to VCC, and the sliding end of the sliding resistor R10 is grounded.

The maximum value of the sliding resistance R10 is 5000 ohms, the capacitor C11=104uF, the capacitor C21=0.1uF, and the resistor R21=5000 ohms.

P5, P3, and P4 are pin headers. P5 pin headers 1 and 2 are connected through a jumper cap. Change the sliding rheostat R10 to change the amplifier gain. Pin header P3 is the 5V power inlet. 2 in the pin header P2 is the ground wire interface, and 1 in the pin header P2 is disconnected and not used.

Further, the gain adjustable circuit includes resistor R11, capacitor C20, capacitor C18, capacitor C14, resistor R17, resistor R15, capacitor C19, resistor R19, capacitor C16, P4 pin header, resistor R13, resistor R14, capacitor C17, P7 pin row, capacitor C12, capacitor C13, capacitor CD1, inductance coil L2 and P3 pin row, the MODE port of the AD8367 chip is connected in series with the resistor R11 and resistor R13 to the VPSI port of the AD8367 chip, between the resistor R11 and the resistor R13 The node between the nodes is connected in series with the capacitor C14 to ground, the node between the resistor R11 and the resistor R13 is connected to VCC, the VPSI port of the AD8367 chip is connected to the ground after the capacitor C16 is connected in series, and the VPSO port of the AD8367 chip is connected in series with the resistor R14 to VCC. The VPSO port of the AD8367 chip is connected in series with capacitor C17 and then grounded; VCC is connected in series with capacitor C12 and then grounded. Capacitor C13 and capacitor CD1 are respectively connected in parallel at both ends of capacitor C12. Port 1 is connected to port 2 of the P3 pin header.

Resistor R11=10KΩ, capacitor C20=10nF, capacitor C18=10uF, capacitor C14=1uF, resistor R17, resistor R15=100Ω, capacitor C19=0.1uF=capacitor C17, resistor R19=57.6Ω, capacitor C16=0.1uF, resistor R13=4.7Ω=resistor R14, capacitor C12=101uF, capacitor C13=104uF, capacitor CD1=10uF.

Further, the seventh-order LC passive filter circuit includes IN1 interface, OUT1 interface, resistor R31, capacitor Cap1, capacitor Cap2, capacitor Cap3, capacitor Cap4, capacitor C31, capacitor C36, capacitor C37, inductance coil L3, inductance coil L4 , inductance coil L5, inductance coil L6, inductance coil L7, inductance coil L8, inductance coil L9, resistor R32, the central node of the IN1 interface is connected in series with resistor R31, inductance coil L7, inductance coil L3, inductance coil L8, inductance coil L4, The inductance coil L9, the inductance coil L6, the central node of the OUT1 interface, the peripheral metal of the IN1 interface, and the peripheral metal of the OUT1 interface are grounded, the node between the inductance coil L6 and the central node of the OUT1 interface is connected in series with the capacitor Cap4 and grounded, and the resistor R32 is connected in parallel Both ends of capacitor Cap4, capacitor C31 are connected in parallel at both ends of inductance coil L7 and inductance coil L3, capacitor C36 is connected in parallel at both ends of inductance coil L8 and inductance coil L4, capacitor C37 is connected in parallel at both ends of inductance coil L9 and inductance coil L6, and inductance coil L8 The node between the inductance coil L3 and the inductance coil L3 is connected in series with the capacitor Cap2 and then grounded, the node between the inductance coil L9 and the inductance coil L4 is connected in series with the capacitor Cap3 and then grounded, and the P7 interface is connected to the IN1 interface.

Resistor R31=0 ohms, capacitor Cap1=56pF, capacitor Cap2=276PpF=capacitor Cap3, capacitor Cap4=68pF, capacitor C31=62nF, capacitor C32=23nF, capacitor C33=493nF, resistor R32=49.9 ohms.

Further, the attenuation circuit includes an IN2 interface, a capacitor C0, an HMC470 chip, a capacitor C9, a capacitor C8, and a capacitor C7. The central node of the IN2 interface is connected to the RF1 port of the HMC470 chip after the central node of the IN2 interface is connected to the RF1 port of the HMC470 chip. The peripheral metal of the IN2 interface is grounded, and the HMC470 The VDD port of the chip is connected to +5V, the VDD port of the HMC470 chip is connected in series with the capacitor C7 and grounded, the capacitor C8 and the capacitor C9 are respectively connected in parallel at both ends of the capacitor C7, and the OUT1 interface is connected to the IN2 interface.

Capacitor C0=0.1uF=capacitor C7, capacitor C9=10uF=capacitor C8.

Further, the attenuation circuit includes a P8 DIP switch, a pull-up resistor, a capacitor C36, a capacitor C37, a capacitor C34, and a capacitor C35. The 2 ports, 4 ports, 6 ports, 8 ports and 10 ports of the P8 DIP switch are respectively Connect the left end of the pull-up resistor, the right end of the pull-up resistor is connected to +5V; the 10 port of the P8 DIP switch is connected to the V1 port of the HMC470 chip, the 8 port of the P8 DIP switch is connected to the V2 port of the HMC470 chip, and the P8 DIP switch The 6 ports of the P8 DIP switch are connected to the V3 port of the HMC470 chip, the 4 ports of the P8 DIP switch are connected to the V4 port of the HMC470 chip, the 2 ports of the P8 DIP switch are connected to the V5 port of the HMC470 chip, the NC port of the HMC470 chip is grounded; the AGC6 port of the HMC470 chip After the series capacitor C35 is grounded, the GND port of the HMC470 chip is grounded, the AGC5 port of the HMC470 chip is grounded after the series capacitor C34, the AGC4 port of the HMC470 chip is grounded after the series capacitor C37, the AGC3 port of the HMC470 chip is grounded after the series capacitor C36, and the AGC2 of the HMC470 chip Port, the AGC1 port of the HMC470 chip is connected to the AGC3 port of the HMC470 chip.

Capacitance C36=330Pf=capacity C37=capacity C34=capacity C35.

P8 is a DIP switch. There are 5 switches on it. The attenuation multiple of the circuit composed of the HMC470 chip can be changed by different combinations of on and off of the 5 switches, so as to realize the attenuation of different multiples of the signal.

Further, the attenuation circuit includes a capacitor C6 and an OUT2 interface, and the RF2 port of the HMC470 chip is connected in series with the capacitor C6 and OUT2 and grounded.

Further, VCC is +5V power supply.

This broadband amplifier uses high-speed operational amplifier OPA690, high-performance variable gain amplifier AD8367, and attenuator HMC470 as the main chip, and designs a single power supply, 1MHz-40MHz bandwidth, and 0~40dB gain adjustable amplifier circuit.

With high-speed operational amplifier OPA690, high-performance variable gain amplifier AD8367, and attenuator HMC470 as the core, OPA690 is used as the pre-stage fixed gain circuit of the entire amplifier, AD8367 is used as an intermediate stage to achieve adjustable gain, and HMC470 is used as a radio frequency attenuator to adjust gain of the entire circuit. All chips operate from a single supply. Can realize 1MHz-40MHz bandwidth, 0~40dB gain adjustable. The amplifier input and output loads are both 600 ohms.

The pre-stage adopts OPA690 chip to achieve a fixed 8-fold gain. OPA690 is a current-type high-speed operational amplifier with a high slew rate of 4300V/us, a maximum output current of 120mA, and a minimum input signal of 1mVpp, which can amplify small signals and avoid entering The voltage of the voltage-controlled amplifier is too small to realize the amplification problem.

The intermediate stage adopts AD8367 to achieve adjustable gain. AD8367 is a high-performance VGA chip, using a single +5V power supply, the gain can be adjusted in the range of -2.5dB-42.5dB, the input impedance is 200Ω, the output impedance is 50Ω, the gain control characteristic is linear in dB, and the amplifier voltage can be realized continuous control.

The post-stage attenuator uses HMC470 as the main control chip. HMC470 is a 5-bit GaAs IC digital attenuator with an attenuation multiple of 0-31dB and a step size of 1dB. The corresponding attenuation multiple is controlled by a dial switch with high attenuation accuracy and step The error is small. The pre-amplification circuit cooperates with the attenuator to realize the output of small signal.

A 7th-order LC passive bandpass filter is added to the system, and the LC passive filter is used to avoid the problem of low cut-off frequency of the active filter. The Butterworth type passive filter is used to make the passband within the circuit 1M-40M It is more flat, the amplifier bandwidth is 1MHz-40MHz, the gain fluctuation in the passband is small, and the -3dB attenuation is realized at 1MHz and 40MHz.

Based on the design principles of single power supply, wide bandwidth and high gain, the system selects high-performance chips with single power supply, wide bandwidth and low noise. Anti-interference measures such as capacitive decoupling and filtering are comprehensively applied to reduce amplifier noise and suppress high-frequency self-excitation. The whole system has simple structure and superior performance.

At present, there are many program-controlled amplifiers that use dual power supplies, but single power supplies are relatively rare. The circuit proposed by the utility model is suitable for use in some portable instruments or general electronic measuring instruments.

The pre-stage circuit uses OPA690 for fixed-gain amplification, and cooperates with the post-stage voltage-controlled amplifier to achieve small signal amplification. A 7th-order LC Butterworth passive filter is added to the interstage circuit to realize the bandwidth of the amplifier 1M-40M. Using high-performance VGA chip and HMC470 attenuator, it can realize 0~40dB gain adjustable, and can output small signal at the same time. This system can realize 0dB gain output of 2mV signal, and the maximum undistorted output voltage peak-to-peak value can reach 4.2Vpp. The circuit adopts low-noise chips, and the impedance matching between stages effectively reduces the system noise. The amplifier can output signals with a bandwidth of 1MHz-40MHz without distortion.

The designed circuit only needs a single working power supply of +5V, which has low requirements on the power supply and can reduce the workload of power supply design in the electronic system. Avoid the problem of low efficiency when using DC-DC chips to obtain positive and negative power supplies.

(1) The system circuits are all high-precision analog circuits, and the entire system is powered by a single +5V power supply. +5V is used as the working power supply of fixed amplifier stage, adjustable gain stage, filter and attenuator.

(2) As shown in Figure 1, the system consists of four parts: OPA690 fixed gain circuit, AD8367 gain adjustable circuit, passive bandpass filter, and HMC470 RF attenuator. The input signal of the signal source is output to the oscilloscope after passing through the multi-stage circuit Perform a signal test. The AC coupling between stages is carried out through capacitors, which avoids the problem of signal distortion due to the amplification of DC signals. Impedance matching is performed between the stages, and the connection is made through the SMA interface and the shielded wire to ensure the flatness in the passband.

(3) This system uses the low-noise high-speed operational amplifier OPA690 for fixed amplification. The circuit diagram of OPA690 is shown in Figure 2. The signal source is connected to the SMA interface P2 of the amplifier through a shielded wire for signal input, and the amplified signal is output through the SMA interface P1. . Cooperating with the high-performance VGA chip AD8367, the gain can be continuously adjusted, and the pre-stage fixed amplifier of the OPA690 enables the circuit to amplify weak signals. The HMC470 high-bandwidth attenuator used in the rear stage can attenuate large signals, so that the amplifier can output weak signals, and realize 0dB attenuation of weak signals and continuous adjustment of 0dB-40dB.

(4) As shown in Figure 3, the gain adjustable circuit adopts AD8367, the output signal of the OPA690 fixed amplifier is connected to the AD8367 input P6 through the P1 terminal through the shielded wire, and the AD8367 circuit can be connected to the 1 and 2 ports of P2 through the jumper cap. The gain is adjustable or connected to ports 2 and 3 of P2 to select a fixed gain. The utility model connects ports 1 and 2 of P1 to select a gain-adjustable mode through a jumper cap, and realizes gain-adjustable mode by adjusting the sliding rheostat R10. P3 is connected to the power supply to supply power to the circuit, P4 is disconnected, and the signal is output through port P7.

(5) The 7th-order LC filter circuit is shown in Figure 4. The input terminal IN of the 7th-order LC filter circuit is connected to the output terminal P7 of the AD8367 gain adjustable circuit, and the filtered signal is output through the output terminal OUT2.

(6) Attenuation circuit The HMC470 circuit diagram is shown in Figure 5. The input terminal IN2 is connected to the output terminal IN1 of the 7th-order LC filter circuit, and the signal is output through the output terminal OUT1. P8 is a DIP switch with five switches, and the attenuation multiple is controlled by the DIP switch. Labels V1, V2, V3, V4, and V5 represent that the marked pins of dial P8 are respectively connected to pins 12, 13, 14, 15, and 16 of the HMC470 chip.

(7) In the LC filter circuit, the resistors R1 and R2 play the role of impedance matching between the front and rear stages. Write the system function through the required cut-off frequency meter, and calculate the inductance and capacitance values.

(8) The SMA interface is a threaded interface. The inner diameter of the outer conductor is 4.13mm and the maximum transmission frequency is 18GHz. It is connected through a shielded wire to reduce external interference.

(9) Passive Butterworth filter, with its flat passband characteristics, considerable stopband attenuation speed, and "clean" stopband characteristics, has been widely used in actual circuit design. Therefore, this system uses a 7th-order LC passive Butterworth filter to ensure the flatness in the 1M-40M passband, and realize the -3dB attenuation of 1M and 40M, as shown in Figure 6.

The above is only the preferred embodiment of the utility model, and it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the utility model, some improvements and deformations can also be made. And deformation should also be regarded as the protection scope of the present utility model.

Claims (10)

1. a gain-adjustable broadband amplifier of a single power supply, is characterized in that, comprises pre-stage fixed amplifying circuit, gain adjustable circuit, seven-order LC passive filter circuit and attenuation circuit, described pre-stage fixed amplifying circuit The input terminal is connected to the input signal, the output terminal of the pre-stage fixed amplifier circuit is connected to the input terminal of the gain adjustable circuit, and the output terminal of the gain adjustable circuit is connected to the input terminal of the seventh-order LC passive filter circuit, The output end of the seventh-order LC passive filter circuit is connected to the input end of the attenuation circuit. 2. The gain-adjustable broadband amplifier of a kind of single power supply according to claim 1, is characterized in that, described pre-stage fixed amplifying circuit comprises P1 interface, P2 interface, resistance R1, resistance R2, resistance R3, resistance R4, resistor R5, resistor R7, resistor R8, OPA690 chip, capacitor C1, the -IN port of the OPA690 chip is connected in series with resistor R2 and grounded, and the +IN port of OPA690 chip is connected in series with resistor R5, capacitor C1, and resistor R7 in sequence, then grounded, and the input signal Connect the node between the capacitor C1 and the resistor R7 through the central node of the P2 interface, the peripheral metal of the P2 interface is grounded, the node between the resistor R5 and the capacitor C1 is connected in series with the resistor R8 and grounded; the -Vs port of the OPA690 chip is grounded, and the -Vs port of the OPA690 chip The +Vs port is connected to VCC, the VOUT port of the OPA690 chip is connected to the -IN port of the OPA690 chip in series with resistor R1, the VOUT port of the OPA690 chip is connected in series with resistors R3, R4 and the central node of the P1 interface, and the peripheral metal of the P1 interface is grounded. 3. the adjustable gain broadband amplifier of a kind of single power supply according to claim 2, is characterized in that, described gain adjustable circuit comprises P6 interface, resistance R18, resistance R16, AD8367 chip, the AD8367 chip The INPT port is connected to the central node of the P6 interface after being connected in series with the resistor R16, the peripheral metal of the P6 interface is grounded, the node between the resistor R16 and the P6 interface is connected in series with the resistor R18 and grounded, and the P6 interface is connected to the P1 interface. 4. A single-power-supplied gain-adjustable broadband amplifier according to claim 3, wherein the gain-adjustable circuit comprises a sliding resistor R10, an inductance coil L1, a pin header of P5, a capacitor C11, and a capacitor C21 , resistance R21, the GAIN port of the AD8367 chip is connected to the 2 ports of the P5 pin header, the DETO port of the AD8367 chip is connected to the 2 ports of the P5 pin header after the capacitor C11 is connected in series, and the DETO port of the AD8367 chip is grounded after the capacitor C21 is connected in series , the two ICOM ports of the AD8367 chip are both grounded, the first port of the P5 pin header is connected in series with the sliding resistor R10, the resistor R21 is connected to VCC, and the sliding end of the sliding resistor R10 is grounded. 5. The gain-adjustable broadband amplifier of a kind of single power supply according to claim 3, is characterized in that, described gain-adjustable circuit comprises resistor R11, capacitor C20, capacitor C18, capacitor C14, resistor R17, resistor R15 , capacitor C19, resistor R19, capacitor C16, P4 pin header, resistor R13, resistor R14, capacitor C17, P7 pin header, capacitor C12, capacitor C13, capacitor CD1, inductor coil L2 and P3 pin header, the AD8367 chip's MODE The port is connected to the VPSI port of the AD8367 chip after connecting the resistor R11 and the resistor R13 in series, the node between the resistor R11 and the resistor R13 is connected to the ground after the capacitor C14 is connected in series, the node between the resistor R11 and the resistor R13 is connected to VCC, and the VPSI of the AD8367 chip is After the port series capacitor C16 is grounded, the VPSO port series resistor R14 of the AD8367 chip is connected to VCC, the VPSO port of the AD8367 chip is connected to the ground after the capacitor C17 is connected in series; the VCC series capacitor C12 is connected to the ground, and the capacitor C13 and the capacitor CD1 are connected in parallel Both ends of the capacitor C12, VCC is connected to the inductance coil L2 and then connected to the 1 port of the P3 pin header, and the 1 port of the P3 pin header is connected to the 2 port of the P3 pin header. 6. The gain-adjustable broadband amplifier of a kind of single power supply according to claim 5, is characterized in that, described seven-order LC passive filter circuit comprises IN1 interface, OUT1 interface, resistance R31, electric capacity Cap1, electric capacity Cap2 , capacitor Cap3, capacitor Cap4, capacitor C31, capacitor C36, capacitor C37, inductor L3, inductor L4, inductor L5, inductor L6, inductor L7, inductor L8, inductor L9, resistor R32, IN1 interface The central node is serially connected with resistor R31, inductance coil L7, inductance coil L3, inductance coil L8, inductance coil L4, inductance coil L9, inductance coil L6, the center node of the OUT1 interface, the peripheral metal of the IN1 interface, and the peripheral metal of the OUT1 interface are grounded. The node between the inductance coil L6 and the central node of the OUT1 interface is connected in series with the capacitor Cap4 and grounded, the resistor R32 is connected in parallel at both ends of the capacitor Cap4, the capacitor C31 is connected in parallel at both ends of the inductance coil L7 and the inductance coil L3, and the capacitor C36 is connected in parallel at both ends of the inductance coil L8 and The two ends of the inductance coil L4, the capacitor C37 is connected in parallel at both ends of the inductance coil L9 and the inductance coil L6, the node between the inductance coil L8 and the inductance coil L3 is connected in series with the capacitor Cap2 and grounded, and the node between the inductance coil L9 and the inductance coil L4 is connected in series with the capacitor After Cap3 is grounded, the P7 interface is connected to the IN1 interface. 7. The gain-adjustable broadband amplifier of a kind of single power supply according to claim 6, is characterized in that, described attenuation circuit comprises IN2 interface, electric capacity C0, HMC470 chip, electric capacity C9, electric capacity C8, electric capacity C7, IN2 The central node of the interface connects the RF1 port of the HMC470 chip in series with the capacitor C0, the peripheral metal of the IN2 interface is grounded, the VDD port of the HMC470 chip is connected to +5V, the VDD port of the HMC470 chip is connected in series with the capacitor C7 and grounded, and the capacitors C8 and C9 are respectively connected in parallel Both ends of the capacitor C7, the OUT1 interface is connected to the IN2 interface. 8. The gain-adjustable broadband amplifier of a kind of single power supply according to claim 7, is characterized in that, described attenuation circuit comprises P8 dial switch, pull-up resistance, electric capacity C36, electric capacity C37, electric capacity C34, Capacitor C35, the 2 port, 4 port, 6 port, 8 port and 10 port of P8 DIP switch are respectively connected to the left end of the pull-up resistor, and the right end of the pull-up resistor is connected to +5V; the 10 port of P8 DIP switch is connected to HMC470 The V1 port of the chip, the 8 ports of the P8 DIP switch are connected to the V2 port of the HMC470 chip, the 6 ports of the P8 DIP switch are connected to the V3 port of the HMC470 chip, the 4 ports of the P8 DIP switch are connected to the V4 port of the HMC470 chip, and the P8 DIP switch The 2 ports of the switch are connected to the V5 port of the HMC470 chip, and the NC port of the HMC470 chip is grounded; the AGC6 port of the HMC470 chip is connected to the ground after the capacitor C35 is connected in series; the GND port of the HMC470 chip is grounded; The AGC4 port is connected in series with the capacitor C37 and grounded, the AGC3 port of the HMC470 chip is connected in series with the capacitor C36 and grounded, and the AGC2 port of the HMC470 chip and the AGC1 port of the HMC470 chip are connected to the AGC3 port of the HMC470 chip. 9. A single-power-supplied gain-adjustable broadband amplifier according to claim 7, wherein the attenuation circuit includes a capacitor C6 and an OUT2 interface, and the RF2 port of the HMC470 chip is connected in series with the capacitor C6 and OUT2 and grounded. 10. A gain-adjustable broadband amplifier powered by a single power supply according to any one of claims 2, 4 and 5, wherein VCC is +5V for power supply.