SU738160A1 - Analogue signal switching device - Google Patents

Description

(54) ANALOTIC SIGNAL SWITCH

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The invention relates to electronic switching devices and can be used in the areas of automatic control of information-measuring systems and data entry systems of the PCLM,

Known switch analog. signals, containing a half current generator connected to a combined output of parallel-connected series-parallel diode switches and an input of differential amplifier 1,

The known switch has a low resistance.

The aim of the invention is to increase the input resistance.

The goal is achieved by commuting analog signals to a switch containing a half-generator. current connected to the combined output of parallel-connected series-parallel diode switches and the input of the differential amplifier, a bit switch, two capacitors, two diodes, low-pass filters and a charge switch are introduced: the transistor of the switch is connected to the combined output parallel-connected parallel-parallel diode switches and the input of a differential amplifier, the second input of which is connected to the single-pin GT1Pkb1SchenN§yr5VT NZhRSHEYY &

5 which through the included counter efSiSoWSTeRrad TtB-a diode-connected

x.v-.iK is the second capacitor, and with the output of the differential amplifier is connected the base of the external transistor, the emitter

10 of which is connected to the control electrode of the discharge of the key, and the collector of the anodes of two diodes, connected to the BCTpe iWb-pd. In this case, at the input of each series-pair} of a dyod key, a low-pass filter is turned on.

The drawing shows the principal electrical circuit of the switch

; analog signals.

20

It contains a generator of 1 half-current, series-parallel, diode switches 2, diodes 3, 4, 5 Shpedovoya-parallepny key / resistor b, filters 7 low frequency,

25 differential amplifier 8, differential capacitors 9, 10, connected in series, diodes 11, 12, bit switch 13, diode 14, charge transistor 15, resistor 16,

thirty

The analog signal switch works as follows.

An analog signal is supplied to the input of diode switch 2 via a low-pass filter 7. As long as a positive control of the pulses is not applied to the cathode of control diode 5, diode 5 is open V. All current from the source through the resistor b flows into this diode due to negative control voltage of diode 3 and 4 are shifted in the opposite direction. In this case, the diode switch 2 is closed and its input resistance is large, since it is due to the reverse current of diode 3.

With the advent of control, the | | th positive pulse Uy ,, p. The diode 5 is closed and all current begins to flow through diode 4. Half of this current is taken by generator 1, and the second half of this current is charged to the parasitic capacitance of the circuit, which is the sum of the total capacitance of the closed channels, the input capacitance of the differential amplifier and the mounting capacitance. It should be noted that the bit switch 13 is closed, and the input current of the differential amplifier 8 is very small. The charge of the parasitic capacitance of the circuit leads to a voltage on one of the inputs of the differential amplifier 8, which in turn causes an imbalance of the input voltages of the differential amplifier 8 and the appearance of a negative voltage at its output. The charging transistor 15 opens and a parallel occurs. capacitors 9 and 10 according to the law, repeating the law of voltage variation on the parasitic capacitance of the circuit. The voltage on the parasitic capacitance increases linearly to a value equal to the magnitude of the input voltage applied to the input of the filter 7, which is equivalent to applying a voltage to the cathode of the diode 3, since the voltage drop across the filter 7 is negligible due to the smallness of the flowing current. .

At the moment of equality of the values of the voltage on the parasitic capacitance and the input voltage, the charge of the parasitic capacitance ceases due to the fact that half of the current begins to flow through the diode 3 that has opened i this moment into the filter circuit 7 of the low frequency. The termination of the charge of the parasitic capacitance leads to the appearance at the output of the differential amplifier 8 and the emitter of the charging transistor 15 a positive voltage front and, consequently, to the termination of the charge of the capacitors 9 and 10 and the opening of the discharge switch 13. The closure of the discharge switch 13 leads to an instantaneous discharge the parasitic capacitance and the capacitor 9. The capacitor 10 is not discharged, remember the output voltage of the switch, equal to the input voltage of the channel in question.

The closure of the bit switch 13 also leads to instantaneous switching of the bias current from diode 3 to diode 4 and bit 13, so that the current in the low-frequency filter circuit runs for a very short time, determined by the ratio of the switching voltage of the diode pair 3- 4 to the rate of increase of voltage on stray capacitance. Since the low-pass filter 7 performs integration (smoothing) of current pulses arriving

5 into it from the side of diode 3, a constant input current will flow in the input circuit, the magnitude of which is only once less than the amplitude of the pulse current, and how much the switching time is less than the polling period of the given channel.

The magnitude of the DC current flowing in the input circuit determines the value of the input resistance

5 each of the channels of the switch.

Claims (1)

1. Patent of Great Britain No. 1043569 NRT / 08.04.68 (prototype). II -T-