SU491189A1 - Amplifier - Google Patents

Description

The invention relates to radio engineering, can be used to amplify audio signals in radio equipment for various purposes.

It is known a power amplifier containing an input transistor, the emitter of which is connected to the emitter of the first) Output transistor directly, and its base through opposite-connected zener diodes, the connection point of which is connected to the collector of the second output transistor.

The purpose of the invention is to reduce the iB distortions of a region of large | THEIR signals.

For this purpose, an additional transistor is introduced into the proposed amplifier, the emntter junction of which is connected in parallel to the collector resistor of the input transistor, and the base through the additionally inserted resistor of the voltage divider is connected to the connection point of the emitters of the input and first output transistors.

The drawing shows a diagram of the device.

The amplifier is built on four transistors: an input /, a switch, a circuit with a common emitter, two input 2 and 5, connected according to a circuit with a common emitter and a common collector, respectively, and an additional transistor 4, connected according to a circuit with a common emitter.

The base of the transistor / is connected to the input of the amplifier, and its emitter is connected to the output of the amplifier. The collector of the transistor / is connected directly to the base of the transistor 2 and the collector of the additional transistor 4, and through a resistor 5 to the output of the power source b. In addition, the emitters of transistors 2 and 4 are connected to the power supply pole. The base of transistor 4 is connected to the output of the amplifier through resistor 7, and through a resistor 8 to the output of power supply 6. The collector of transistor 2 is connected to the base and emitter of transistor 3 via stabilizers 9 and 10 respectively. In parallel, the Zener diode 10 is enabled resistor 11.

The base of the transistor 3 is connected via two B1 connected resistors 12 and 13 in series to the power supply terminal 14. The same terminal is connected to the collector of transistor 3. The common point of the resistors 12 and 13 is connected through the condenser O: p 15 to the output of the amplifier.

In the rest mode, transistors 1 and 3 are determined by the voltage at the base-emitter section of transistor 2 and the collector current of transistor 4, 1 which is set using resistors 5, 7 and S and the voltage at the base-emitter section of transistor 2.

The quiescent current of transistor 2 is determined by resistors 12 and 13 and a bias circuit connected to the input of the amplifier. j

The voltage on the –stable 9 is chosen to be close to the voltage in the base-emitter transistor section: a 3. If it exceeds slightly in absolute value, voltage, transistor 5 base-emitter section, flows through the resistor // the current is in the direction from the emitter of the pre-switch 3 to the collector of transistor 2. At the same time, the zener diode 10 should not be punctured.

The current drift of loco transistors 1-3 is compensated for in the dongle amplifier in the same way as in the known one. The drift of the quiescent current of transistor 4 is compensated for by changing the quiescent currents of the transistors /, and 3. To eliminate this drift, transistor 4 can be closed in quiescent mode by selecting a resistor 8. The base of the transistor 4 must be connected to the output of the amplifier via an additional resistor and a capacitor connected in series.

In dIiA.micheoko: M mode lr. And the amplifier operates in the small signal area, nonlinear distortions are reduced by choosing a small resistance of resistor 11 with voltage compensation in the base-emitter section of transistor 3 using zener diode 9.

YlipH operation of the amplifier in the region of a large signal in the negative half-period of the output transistors /, and 2, Zener diode W is broken. The current through the resistor 7 is reduced, the transistors 4 VI 3 are closed and do not affect the operation of the amplifier. In the other half-period on the amplifier output, transistors 1-4 work.

During this period, as the emitter current of the transistor 3 increases, the current through the resistor 6 and the collector current tr, of the anzistor 4 increase. At the same time, the emitter current of the transistor / increases by the amount of change in the collector current of transistor 4.

An increase in the current through the transistor /, which is included in the IB negative feedback loop according to a common base circuit, is equivalent to reducing the overall resistance of the base transistor / .and corresponding to an increase in the current gain

four

the input stage in the circuit, which approaches in this case the current gain factor.

The current gain in the loop of the transistor / can be taken into account in the gain (Kiz) of the current in the loop of transistor 3, which is derived from:

one

N / A

. ()

b L / 4

Rf is the resistance of the signal source;

;

Ro is the base circuit resistance for the output transistor 3;

/ Ci4 is the gain of the cascade current on the additional transistor 4;

and gz are the gain factors of the transistors / and 5 in the circuit with a common base.

In connection with this, the depth of the negative feedback of the ZI in the loop, which includes transistors 1–3, increases, which reduces the distortion of the amplifier in the region of a large signal.

Claims (1)

Invention Formula A power amplifier containing an input transistor, the emitter of which is connected to the emitter of the first output transistor, and to its base through counter-connected zener diodes, exactly: how many connections are connected to the collector of the second output transistor, characterized in that in order to reduce distortion in the field of large signals, an additional transistor is introduced into it, the emitter-collector junction of which is connected in parallel to the collector resistor of the input transistor, and the base is additionally connected the voltage divider resistor is connected to the junction point of the emitters of the input and the first output transistors. t Code 0 6-7