CN101807884A - Feed-forward noise cancellation resistance negative feedback broadband low noise amplifier - Google Patents

Abstract

The invention belongs to the technical field of integrated circuit design. Specifically, it is a broadband low-noise amplifier improved by using the feed-forward noise cancellation technology. The circuit structure in the present invention combines the two technologies of parallel negative feedback and noise cancellation, and integrates the two together. On the basis of the traditional resistance negative feedback low noise amplifier, an amplification path for signal and noise voltage is added to reach the inside of the circuit. The noise voltages of the nodes cancel each other out, while the signal voltage is increased, the output noise current is reduced, and finally the output noise voltage is reduced, and the noise figure of the low noise amplifier is reduced, thereby improving the sensitivity performance of the receiver. The invention realizes a resistor negative feedback broadband low noise amplifier circuit structure.

Description

Feedforward Noise Cancellation Resistor Negative Feedback Wideband Low Noise Amplifier

technical field

The invention belongs to the technical field of integrated circuit design. In particular, it relates to a broadband low noise amplifier in a wireless communication system receiver.

Background technique

In the case of amplifying weak signals, the noise of the amplifier itself may seriously interfere with the signal, so it is desirable to reduce this noise to improve the output signal-to-noise ratio. An essential building block for almost all RF receiver systems is the Low Noise Amplifier. The main purpose of the low-noise amplifier is: 1. The amplitude of the radio frequency signal received by the system is usually very weak, and it needs to be amplified at the receiving front end before it can be processed correctly; 2. Using an amplifier at the front end of the receiver can effectively alleviate the impact on the subsequent module. Noise performance requirements, reducing the difficulty of post-stage module design. Low-noise amplifiers have different design requirements in different systems. Usually, they can be divided into three types: narrow-band low-noise amplifiers, multi-band low-noise amplifiers and wide-band low-noise amplifiers according to different application frequencies. Regardless of the type of LNA, its main performance indicators include impedance matching, noise figure (NF, Noise Figure), linearity (IIP3, IIP2, 1dB compression point), power consumption, etc. Figure 1 illustrates the role played by the low-noise amplifier 2 in the wireless communication receiving system. It is a bridge between the band-pass filter 1 and the down-conversion mixer 3. After the band-pass filter 1 selects an appropriate frequency band After the signal is amplified by the low-noise amplifier, it enters the mixer and down-converts to an intermediate frequency. The low-noise amplifier (2) can reduce the noise contribution of the subsequent stage circuit, reduce the noise figure of the receiver system, and improve the signal-to-noise ratio and sensitivity.

The noise performance and power consumption of narrow-band low-noise amplifiers are better than those of wide-band low-noise amplifiers, but they can only be used in specific frequency bands. For multi-mode receivers that are increasingly in demand, multiple narrow-band low-noise amplifiers are required, consuming The chip area is large. The advancement of CMOS technology has enabled the design of wideband low noise amplifiers to meet the reception of all signals in the ultra-wideband range, which is suitable for the application of multimode transceivers and software radios. However, compared with narrowband low noise amplifiers, the traditional wideband low noise amplifiers Noise performance is far inferior to narrowband LNAs. The invention combines noise canceling and resistance negative feedback technology to propose a circuit structure of a broadband low-noise amplifier, and realizes a low-noise amplifier with low-noise performance under low power consumption.

Contents of the invention

The object of the present invention is to propose a circuit structure of a novel broadband low noise amplifier. It reduces the noise figure of wideband LNAs and improves gain and linearity performance.

The low noise amplifier proposed by the present invention includes signal source (1), signal source impedance (3), forward gain stage G (2), common source or common emitter amplifier tube M _N1 (5), common grid common source Or common base common header M _N2 (6), load resistor _RL (8), feedback follower (9), feedback resistor R _F (4), channel thermal noise source (7). The connection relationship of the circuit is shown in Figure 2. The input signal is connected to the grid or base of the common-source or common-emitter amplifier tube M _N1 (5), and connected to the input terminal of the forward gain stage G(2), after being amplified by the forward gain stage G(2) The signal output is connected to the gate of the common grid common source or common base common collector M _N2 (6), forming a feedforward noise canceling path. The source or emitter of the common source or common base collector M _N2 (6) is connected to the drain or collector of the common source or common emitter amplifier M _N1 (5), and the common source or common base The drain or collector of the header M _N2 (6) is connected to the load resistor _RL (8), the other pole of the load resistor _RL (8) is connected to the power supply voltage, the output signal is followed by the feedback follower (9) and then connected to the feedback The resistor R _F (4), and the other pole of the feedback resistor R _F (4) are connected to the input port to form a negative feedback loop.

In this invention, the resistance parallel connection negative feedback structure is adopted to reduce the noise figure and form the input impedance matching.

In this invention, the noise cancellation technology formed by the feedforward path is adopted, and the gain stage G in the feedforward path can be realized by a passive circuit or an active circuit.

In this invention, resistors are used as the load and feedback impedance, which may be composed of fixed resistors, variable resistor arrays composed of switches, or voltage-controlled resistors composed of MOS transistors.

In this invention, the common-source or common-emitter amplifier tube M _N1 (5) may be an NMOS tube, or a PMOS tube, or a combined transconductor that is used in combination.

The invention combines noise cancellation technology and negative feedback to reduce the noise figure of broadband low noise figure.

Description of drawings

Figure 1 is a schematic diagram introducing the application of low noise amplifiers in wireless communication receivers.

Fig. 2 is a schematic diagram of a resistor negative feedback broadband low noise amplifier using feedforward noise cancellation proposed by the present invention.

Fig. 3 is a specific circuit diagram of the resistor negative feedback broadband low noise amplifier using feed-forward noise cancellation proposed by the present invention.

Detailed ways

A specific example of implementing the present invention will be described in detail below in conjunction with FIG. 3 .

In Fig. 3, there is ESD protection composed of diodes (2) and (3) when the input signal source (1) is input into the circuit input to prevent electrostatic breakdown. The input signal passes through the high-pass filter formed by the capacitor C1 (19) and the resistor RB1 (18) and adds a bias voltage to the gate of the amplifier tube MN1 (11), and at the same time passes through the capacitor C2 (4) and the resistor RB2 (17) The formed high-pass filter is input to the gate of the amplifier MP1 (12) after adding the bias voltage, and then input to the common source after the high-pass filter formed by the capacitor C3 (5) and the resistor RB3 (6) adds the bias voltage The gate of the common gate transistor MN2 (15) constitutes a feed-forward path for noise and signals. The load resistor RL (7) is connected between the power supply voltage and the drain of the cascode transistor MN2 (15). The output signal is input to the gate of the common drain tube MN3(8) after passing through the high-pass filter formed by the capacitor C4(14) and the resistor RB4(16), and the bias voltage is added, and MN4(9) provides the common drain tube MN3(8) For the bias current, the feedback resistor RF is connected to the input port and the source of the common drain tube MN3 (8) to provide a feedback current signal, reduce the input impedance, and achieve the purpose of matching the source impedance. The feedback capacitor CF (13) is connected between the source of the common drain tube MN3 (8) and the drain of the amplifier tube MN1 (11) to increase the high-frequency gain and increase the bandwidth.

Due to the existence of the negative feedback loop formed by the common drain tube MN3(8), the feedback resistor RF, and MN4(9), the polarity of the signal voltage between the input node and the drain node of the amplifier tube MN1(11) is opposite, and The noise voltages have the same polarity. The noise and signal feed-forward path composed of capacitor C3(5), resistor RB3(6), and cascode transistor MN2(15) forwardly amplifies the signal and noise to the gate of cascode transistor MN2(15). pole, forming a noise cancellation between the gate and source of the cascode transistor MN2 (15). Combining the two noise reduction methods, coincidence reduces the output noise of the LNA. For the signal voltage, the feed-forward path of noise and signal formed by capacitor C3(5), resistor RB3(6), and cascode tube MN2(15) increases the total equivalent transconductance of the circuit, and the voltage gain increases , so the final noise figure will be greatly reduced.

Claims (4)

1. the circuit of a kind of broadband low-noise amplifier is characterized in that by signal source (1), signal source impedance (3), forward gain stage G (2), common source or common emitter amplifier tube M _N1 (5), Common gate common source or common base common collector M _N2 (6), load resistance R _L (8), feedback follower (9), feedback resistance R _F (4), channel thermal noise source (7); through Resistors are connected in parallel with the negative feedback loop and the noise feedforward path to reduce the noise figure of the amplifier; wherein, the input signal is connected to the gate or base of the common-source or common-emitter amplifier tube M _N1 (5), and connected to the forward gain stage The input terminal of G(2), the signal output after being amplified by the positive gain stage G(2), is connected to the gate of the common grid common source or common base common collector M _N2 (6), forming a feedforward noise canceling path; The source or emitter of the common source or common base collector M _N2 (6) is connected to the drain or collector of the common source or common emitter amplifier M _N1 (5), and the common source or common base The drain or collector of the header M _N2 (6) is connected to the load resistor R _L (8), the other pole of the load resistor R _L (8) is connected to the power supply voltage, and the output signal is followed by the feedback follower (9) and then connected to the feedback The resistor R _F (4), and the other pole of the feedback resistor R _F (4) are connected to the input port to form a negative feedback loop. 2. broadband low noise amplifier according to claim 1, it is characterized in that adopting the noise cancellation technology that feedforward path forms, the gain stage G in the feedforward path is realized by passive circuit, or is realized by active circuit. 3. The broadband low-noise amplifier according to claim 1, characterized in that a resistor is used as the load and feedback impedance, and the resistor is a fixed resistor, or a variable resistor array formed by a switch, or a voltage-controlled resistor formed by a MOS tube . 4. broadband low-noise amplifier according to claim 1, it is characterized in that common source or common emitter amplifying tube M _N1 (5) is NMOS tube, or PMOS tube, or the combination transconductor that both are used together .

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