SU1218445A1 - Amplifier with input current compensation - Google Patents

Abstract

The invention relates to radio engineering and can be used in the input stages of operational amplifiers. A reduction in input current is provided. The structure of the first, second transistors (T 1 and 2 and additional transistors (DT) 6 and 7 is opposite to the structure of the third and fourth T 3 and 4. The collector T 1 is connected to the emitter T 2 and the base of DT 6. Emitters T 1 and DT 6 and 7 connected via a current source 5 to the first power source terminal. A collector T 2, emitters T 3, 4 are connected to the second power supply bus and element 8, a collector DT 6 and base DT 7, is connected to the back of the power supply bus. connected to the collector DT 7. To the bases T 1 and 2 are connected (we collectors, respectively, T 4 and 3. Input signal The output signal is determined by the equality of the base current T 1 and the collector current T 4. To do this, the identical operating modes T 1 and 2 are required, which is ensured by the choice of the current-generating current element 8, as well as modes of operation T 3 and 4,; which is provided by DT 7. / W. F. f-crystals, 2 d. (P

Description

one

The invention relates to radio nicknames and can be used in radio electronic equipment for various purposes, such as in the input stages of operational amplifiers.

The purpose of the invention is to reduce the input current.

FIG. Figure 1 shows a circuit diagram of an amplifier with input current compensation; in fig. 2 is a circuit diagram of one of the implementations of an amplifier with input current compensation.

The amplifier with compensation input-i current (Fig. 1) contains the first,: second, third and fourth transis-, tori 1-4, current source 5, -first and second additional transistors 6 and 7, current-element 8, made ( Fig. 2) on the third and fourth additional transistor ah 9 and 10, diode circuit 11, and

fifth additional transistor 12. I

Amplifier with input current compensation works as follows.

The degree of compensation of the input current is determined by the accuracy of the equality of the base current of the first transistor 1 and the collector current of the fourth transistor 4, and this, in its turn, is determined by the identity of the operating modes of the first and second transistors 1 and 2, and the third and fourth transistors 3 and 4. The last pair of transistors is in almost identical conditions (the difference between the emitter-collector voltages of these transistors, the base-emitter voltage of the second transistor 2 can be eliminated by including ornuyu circuit 4 of the fourth transistor mosmeschennogo diode etc.); Therefore, if we ensure the identity of the modes of the first and second .. transistors 1 and 2, it is possible to achieve full compensation of the input current of the amplifier with compensation of the input current. The equality of the collector-emitter voltages of these transistors can be achieved by choosing the magnitude of the positive (for a given pattern) voltage of the power supply and providing (external circuits) changing this voltage synchronously

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input signal, or using the structure of the first transistor as an auxiliary transistor, with the first

of the cascade circuit (the second and fifth additional transistor, the additional transistors 2, 12 are connected to the base of the second additional

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five

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five

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five

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and diode circuit 11). The equality of the emitter currents of the first and second transistors 1 and 2 is ensured by the selection of the current – current value of the element 8 equal to the emitter current of the first transistor 1, so that the base current of the first additional transistor 6 is equal to the base current of the first transistor 1. This can be achieved using as a current supply element 8 of the circuit on the third and fourth additional transistors 9 and 10. The base currents of the third and fourth transistors 3 and 4 are provided by the second additional transistor 7, whose modes are This current is adjusted to these base currents by internal negative current feedback. Thus, in this scheme, the choice of the value of the current of the current-generating element 8 can ensure that the operating modes of the first and second transistors 1 and 2 are identical, which ensures the equality of their base currents and, therefore, full compensation of the input current of the circuit.

Claims (2)

1. An input-current-compensated amplifier containing the first transistor, whose base is the input, and the emitter — the output of the amplifier with compensation for the input current and through the current source is connected to the first pin power source, and the collector to the emitter of the second transistor,; the collector of which is connected to the second power supply bus; the base is connected to the collector of the third transistor, the base and emitter of which are connected respectively to the base and emitter of the fourth transistor, the emitters of the third and fourth transistors are connected to the second power supply, the structure of the first and second transistors is opposite to the structure the third and fourth transistors, characterized in that, in order to reduce the input current to the amplifier, a current supply element is introduced, as well as the first and second additional anzistors, the structure of which of the respective transistor and through the current-generating element - with the second bus power source, the base - with the collector, and the emitter - with the emitter of the first transistor to which the emitter of the second additional transistor is connected, the collector of which is connected to the base of the fourth transistor, the collector of which connected to the base of the first transistor. 2. The amplifier according to claim 1, wherein the current-generating element is fulfilled on the third and fourth additional transistors and a diode circuit, one pin of which is the current output element and the other output is connected to the emitter of the third additional transistor, the base of which is connected to the collector of the fourth additional transistor, the emitter of which is connected to the collector of the third additional transistor and to the second power supply bus, and the collector of the second transistor is connected to the second bus of the power source through the emitter, ter - the collector of the fifth additional transistor, whose base is connected to the emitter of the third additional transistor ora About the 8th, VNIIPI Order 1137/59 Circulation 818 Subscription Branch ShP Patent, Uzhgorod, Projecto st., 4 .g