SU1298842A1 - Synchronous detector - Google Patents

Abstract

This invention relates to a measurement technique. The purpose of the invention is to increase the detection accuracy and speed. The device contains an input capacitor 1, resistors 2, 8, 12-14, 16, a capacitor 3, operating level 4, a 5-bit switch, a charging key 6 containing a diode 7 , resistor 8, transistor; the output terminal 10, the diode 11, the transistor 15, the sources 17 and 1B of DC voltage are negative. and positive polarity. The value of the resistor 2 is given by the coefficient. conversion, selection of rated current. Typically, the resistor is 2 (0.6-1.5) kΩ at (3-5) ML. The determining value for a given bias current is the magnitude of the resistor 14. For the normal operation of the device, the following conditions are specified: transistors 15 and 9 are a pair, for example, an IC of type 2TC3103A, resistors 13 and 8 are equal. 1 il. (L you ju with 00 oo NI th 1

Description

The invention relates to measuring technique, spectrometry, and is intended for simultaneous detection with high linearity over a wide dynamic and frequency range of signals.

The purpose of the invention is to improve the detection accuracy and speed.

The drawing shows a functional electrical circuit of a synchronous detector.

The synchronous detector contains an input capacitor 1, the first resistor 2, the capacitor 3, the operational amplifier (op-amp) 4j key 5 bits, the key 6 charge, containing a diode 7, a resistor and a transistor 9, the output terminal 10, the diode 11, the second 12, the third 13 and fourth 14 resistors, a transistor 15, a fifth resistor 16, sources 17 and 18 of a constant voltage of negative and positive polarity, respectively.

Synchronous detector works as follows.

The following conditions are necessary for the normal operation of the synchronous detector: transistors 15 and 9 are a pair (for example, an IC of type 2TC3103A), resistors 13 and 8 are equal.

In the initial state in the absence of an input signal, the potentials of the inputs and. OU 4 outputs are almost equal to the voltage of the source 18 of a constant voltage of positive polarity.

Since there is an input capacitor 1, when Ugj, O, the transistor 9 is closed, and the current from the output of the op-amp 4 for the positive half-period of the input signal flows through the open diode 11 and the resistor 12, while willow about the diode 11 is closed, the current from the output of the op-amp 4 flows through resistor 13 and open TijaHSHCTop 15

Since the resistance values of the resistors 13 and 8 are equal, and the parameters; Transistors 9 and 15 are close enough, the currents flowing through transistors 9 and 15 can be considered equal. Consequently, the capacitor 3 receives a charge proportional to the input current over the negative half period.

The current flowing through the resistor 8 from the output of the op-amp 4 is intercepted by the open diode 7 when it is open and goes to the capacitor 3 when the diode 7 is covered by a positive potential

gating pulse U. Gating signals with a duration of one period of the detected frequency are produced by external devices.

When bfu 0, the transistor 15 is open, a current flowing through it (and transistor 9) is equal to the current of resistor 2. This current is the sum of the signal current and the bias current.

The magnitude of the resistor 2 is determined by the conversion factor, the selection of the rated current, etc. Usually the value of the resistor is 2 0.6-1.5 kΩ at 3-5 MA. Therefore, the value of the resistor 14 serves as the determining factor for the given bias current.

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Claims (1)

Invention Formula A synchronous detector containing a series-connected input capacitor and a first resistor, an operational amplifier, a parallel-connected capacitor and a discharge key, and also a switch whose output is connected to the connection point of the capacitor with the discharge key, characterized in that; to increase detection accuracy and speed, sources are introduced (positive and negative polarity voltage, a diode connected in series, the anode of which is connected to the inverting input of the operational amplifier, the second and third resistors, the connection point of which is connected to the output of the operational amplifier, the transistor, the emitter of which is connected to another output of the third resistor, the collector is with the inverting input of the operational amplifier, and the base is connected to a source of a DC voltage of positive polarity, the fourth resistor connected between the connection point of the input capacitor to the first resistor and a source of DC voltage positive polarity, fifth resistor connected between the connection point of the cathode of the diode with the second resistor and a source of direct voltage, negative polarity, while the charge key contains a diode whose cathode is a control input, a transistor whose emitter is connected to the anode of the diode and one pin of the resistor, the other pin of which is 312988424 the input of the charging key, the collector of positive polarity, the other point of the output of the charging key, and the base of the connection of the capacitor with the key is connected to the source of voltage across the common bus.