SU1282309A1 - High-frequency amplifier - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to expand the bandwidth, increase the output power and decrease the output resistance of the UHF. UHF contains three transistors (T) 1-3, four capacitors 4.8-10, resistive divider 5, common bus 6, three resistors 7.11 and 13, power supply bus 12, secondary input winding 14 and parallel RC - chain 15. The 1st stage on T 1 is made according to a circuit with a divided load. T 1 is switched on, according to the scheme with a common emitter, which explains the high coefficient of the 1st stage. The signal applied to bases T 2 and 3 is amplified and fed to the transmitter by the collector. Thus, in the circuit, all active elements operate on a common load in parallel. T 2 and 3 are included according to the scheme with a common collector, the output conductivity of which has an inductive reactive component of southeastern. The output conductance of the 1st stage on T 1 has a capacitive reactive component. As a result, the output and input reactivity cancel each other out, which leads to an increase in the passband towards the RF. 1 il. FT € (lu 00 to co o; o

Description

The invention relates to radio engineering and can be used to amplify high frequencies in radio receiving, radio transmitting and other devices.

The purpose of the invention is to expand the bandwidth, increase the output power and decrease the output impedance of the high frequency amplifier.

The drawing shows a circuit diagram of the proposed high frequency amplifier.

The high-frequency amplifier contains the first, second and third transistors 1-3, the first capacitor 4, the resistive divider 5, the common bus 6, the first resistor 7, the second, third and fourth capacitors 8-10, the second resistor 11, the bus 12 power sources, third resistor 13 ,. the secondary winding 14 of the input transformer and the parallel RC-chain 15.

The high-frequency amplifier works as follows.

The input signal from the secondary winding 14 of the output transformer is fed through the first and third capacitors 4 and 9 to the emitter junction of the first transistor. In this case, the primary winding of the input transformer forms an LC circuit. The collector of the first transistor 1 is connected via the second capacitor 8 to the downstream bus, and the first resistor 7 is connected to the emitter circuit, part of the amplified signal is fed to the base of the second transistor 2 and through the third capacitor 9 to the base of the third transistor 3.

Thus, the first stage of the first transistor 1 is made according to a split-load circuit: a part of the amplified signal is fed directly from the collector to the output bus, and the other part to the bases of the second and third transistors 2 and 3 of the output stage. Since the common electrode between the input and the output of the first transistor 1 is an emitter, it turns out to be connected according to the common emitter (OE) circuit, which explains the high gain of the first stage.

The signal applied to the bases of the second and third transistors 2 and 3 is amplified and c, the collectors are fed to the output, thus the circuit operates in parallel

all active elements on the total load.

The emitters of the second and third transistors 2 and 3 through the capacitor

parallel RC chains 15 and a fourth capacitor 10, respectively, are connected in high frequency to a common bus. However, these transistors are connected in a circuit with a common collector (OC), since the input signal acts between the collectors and emitters of these transistors and the common electrodes between the inputs and outputs are collectors. The output conductivity of transistors connected according to the OK circuit has an inductive reactive component, and in the proposed scheme, parallel to it, the output conductivity of the first cascade OE is connected to the first transistor 1, which has a capacitive reactive component. As a result, the output and input reactivity are mutually compensated, which leads to an increase in the bandwidth of the amplifier to a high frequency side.

Equivalent conductivity | high frequency amplifier can be written as follows

f .Xii

22EKY. Y + Y / 2

five

11 2 U

. Y + Y / 2

Y / g

l

yif + U / 2

0

five

where Y.g parameters of the first, second and third transistors 1-3 in the case of their identity;

Y is the total conductivity of resistors connected to the bases of the second and third transistors 2 and 3.

If you select a specific value - the conductivity Y, you can get a reactive component, e In this case, the active component of the output impedance is 10 - 80 Ohms. In particular, it is possible to choose such a mode of the circuit that in the operating frequency band the condition of matching with the cable impedance will be fulfilled without any special matching circuits.

Claims (1)

Invention Formula A high-frequency amplifier containing the first and second transistors of one structure and the third transistor of another structure, with the base of the first transistor connected to the first terminal of the first capacitor and connected to the resistor splitter, the first terminal of which is connected to the common bus, the emitter of the first transistor and through the first resistor is connected to the common bus, the collectors of the second and third transistors are connected to the first output of the second capacitor, the second output of which is ow. output of the high frequency amplifier, between the bases of the second and third fO J5 check to the common bus and through the second resistor to the power supply bus while the base of the third transistor is connected to the first pin of the third resistor, characterized in that in order to expand the passband, increase the output power and decrease the output resistance, between the base of the third transistor the secondary winding of the input transformer is connected to the second output of the first capacitor, the base of the third transistor is connected to the second output of the resistive divider, the collector of the first transistor is connected to the collector of the second transistor, the second output of the third resistor is connected to the power supply bus, between the emitter The third capacitor of the second transistor is connected to the transistors, and the common controller is connected to the RC controller, the third transistor emitter is connected to the kidney via the fourth capacitor. check to the common bus and through the second resistor to the power supply bus, while the base of the third transistor is connected to the first pin of the third resistor, characterized in that, in order to expand the passband, increase the output power and reduce the output resistance, between the base of the third transistor and the second output of the first capacitor is connected to the secondary winding of the input transformer, the base of the third transistor is connected to the second output of the resistive divider, the collector of the first transistor is connected to the collector W transistor, the second output of the third resistor is connected to the power supply bus, between the emitter Noah included kidney.