SU1517125A1 - Device for switching analog signals - Google Patents

Abstract

The invention relates to radio engineering and can be used in electronic devices for switching alternating voltage signals. The purpose of the invention is to reduce the distortion of the output signal. The goal is achieved by introducing an additional transistor into the differential amplifier, connected in parallel with the collector junction of the transistor amplifier and operating in the emitter follower mode, and an adder on which the switching pulses are destroyed and the useful signal is fed to the output bus without distortion. 2 Il.

Description

The invention relates to electronic engineering and can be used to switch analog signals.

The purpose of the invention is to reduce the influence of the control voltage in the output signal and to ensure that the output signal is matched to the low-impedance load.

Figure 1 presents the scheme of the switch analog signals; figure 2 - diagram of the adder.

The analog signal switch contains a differential amplifier 1 (RC), an emitter follower 2 on an additional transistor connected by a collector-emitter junction parallel to resistor 3, and an adder 4, one input 5 of which is connected to the output of the emitter follower and to the collector of the left transistor, second entrance 6

the adder is connected to the collector of the right transistor of the differential amplifier, which through a resistor 7 is connected to the positive power supply bus.

The differential amplifier operates in current switching mode, i.e. when, the current of 1d, which is determined by the current generator, flows through the left shoulder (DL), the transistor of the right shoulder is closed, when, o, n, vice versa: the current I flows through the right shoulder, the transistor of the left shoulder of the remote control is closed.

The property of switching the currents of the differential amplifier from one arm to the other is used in the proposed switchboard for switching analog signals. For this purpose, parallel to the collector resistor of any transistor (DU) is connected

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loglitelayly.and trlnzistor, ypoli yuuii function emitter repeater

In the proposed scheme, the collector-emitter spine transition is connected in parallel to the resistor 3, the additional compressor bus is connected via a coupling capacitor to the input bus signal. In addition, an offset is applied to the base, which is selected from the count, the offset must provide the max and the shift. } the transistor, or this, the current must be determined by the current generator, and the bias voltage must be metric less than U the collector of the locked transistor of the left Lule

A switching emitter follower works as follows.

When the transistor is open, the left side of the transistor and some of the current flows through the additional transistor, in this case the additional transistor | the transistor operates as an emitter novoritel An analog signal from the input bus to the adder is transmitted with an emitter follower transfer ratio.

When the left-hand transistor is closed, the voltage on the collector becomes greater than the displacement at the base of the additional transistor and the emitter follower closes, that is, the transfer coefficient of the emitter follower becomes zero.

In view of the fact that in the proposed device the differential amplifier is used as a current switch, the collectors of the transistors 11U form antiphase voltage / dn, which are supplied to the accumulator drives. The adder can be measured by any two signal summation scheme, provided that the adder does not have to interfere with matching the output signal with the low impedance load.

In the proposed device, an adder В, 1П011нен on capacitors and resistors (figure 2), contains -condensers 8 and 9, resistors 10-12 (resistor 12 may be absent if it is less than resistors 10 and 11)

Input 5 is connected to the first output of a (amplifier) 1n amplifier (current switch) and to the emitter follower output. Input 6 is connected to the second output of the differential amplifier (current switch).

As is well known, at the outputs of the current switch, antiphase ramps are formed, which, when amplitudes are equal and coefficients are equal, and the summations on the adder are destroyed, an analog signalp is supplied to the output bus from the emitter follower output (Fig. 2).

Thus, the analog signal from the input bus 11 g to the output bus is fed through the emitter follower.

The proposed analog signal switch possesses all the negative-emitter properties of the emitter follower, i.e., it ensures that the switch output is matched with a low-impedance load, besides, it significantly reduces the effect of input control pulses in the output signal.

Claims (1)

Invention Formula An analog signal switch, containing 1Y differential force / body, differential amplifier collectors through the first and second resistors, respectively, are connected to the positive power bus, the base of the right-hand transceiver of the differential amplifier is connected to the zero bus, the base of the left-hand transistor of the differential amplifier is connected to the bus control voltage different By the fact that, in order to reduce the influence of the control voltage in the output signal and to ensure the matching of the output signal with a low-impedance load, additional transistor and su} mat, with the additional transistor collector connected to the positive power bus, the base through the third resistor to the positive power bus, through the fourth the resistor is connected to the zero bus and through the coupling capacitor to the input bus of the signal, the emitter is connected to the collector of the transistor of the left arm of the differential amplifier and the first input of the adder, to the second input of which is connected the collector of the transistor of the right shoulder of the differential amplifier, the output of the adder is connected to the output bus of the device. Jaslg (I oFig .1 12 2