SU1173524A1 - Controlled multivibrator - Google Patents

Abstract

CONTROLLED MULTI-VIBRATOR, containing a symmetric multivibrator with collector-base connections, a transistor with a conductivity type similar to multivibrator transistors, a resistor, a first diode, a first capacitor and the first control signal source, characterized in that, in order to control the frequency of the multivibrator by changing the resistance the time of the master circuit, the second and third diodes are introduced into it, the second capacitor, the second control signal source, and the base of the transistor is connected to a common bus through a resistor Oh and with the anode of the first diode, the collector of the transistor through the first capacitor is connected to a common bus, the emitter through the second capacitor is connected to the collector of a symmetric multivibrator, as well as to the cathodes of the first and second diodes and the anode of the third diode, and the second diode and the cathode of the third diode, respectively but connected to the first and second sources of control signals. (L

Description

The invention relates to a pulse technique and can be used in various electronic devices, where the frequency of a multivibrator must be controlled by a single control pulse.

The purpose of the invention is to control the frequency of the multivibrator by varying the time resistance of the driving circuit.

FIG. 1 shows an electrical circuit of a controlled multivibrator; in fig. 2 - hysteresis characteristic of the dynamic element; in fig. 3 - control pulses (Ui, 1) 2) and pulses at the output of the multivibrator.

The controlled multivibrator (Fig. 1) contains a symmetric multivibrator with collector-base connections, including transistors 1 and 2, resistors 3-6, capacitors 7 and 8 and a source of constant voltage, as well as controlled dynamic element 9, consisting of a transistor 10, a first AND, a second 12 and a third 13 diodes connected by the same terminals to the control pulses and to the base of the transistor 10, the first capacitor 14 connected to the collector circuit of the transistor 10, the second capacitor 15 connected between the multivibrator and the element 9 m, and a resistor 16 to the base circuit of transistor 10, the second terminals of the diodes are combined and connected to the condenser 15.

The device works as follows.

The frequency of the output pulses of a symmetric multivibrator depends on the parameters of the time of the driving circuits. Therefore, when changing the parameters of the elements of the time of the driving circuits, the pulse repetition rate of the multivibrator changes. The element causing a change in the parameters of the time of the driving circuits is the dynamic element 9, the total resistance of which between the capacitor 15 and the total length takes on two values: maximum and minimum. The maximum resistance corresponds to the state “O (disabled)”, and the minimum resistance to the state “1 (enabled)” of the dynamic element. The dynamic element 9 has an S-shaped output characteristic depending on the amplitude of the pulsed supply voltage (Fig. 2). The dynamic element does not contain a constant voltage source.

Let control pulses be absent. In this case, the mode of the transistor 10 depends only on the amplitude of the pulses of a symmetric multivibrator. Positive pulses pass through the circuit capacitor 14 - collector pn junction of transistor 10 - diode 11 - capacitor 15. In this case, capacitor 14 is charged with a minus sign to the collector of transistor 10, and capacitor 15 - a sign "plus to the emitter of the transistor 10 p -pr-type. So

Thus, the condition of the normal switching on of the transistor 10 is created. However, at small values of the amplitude of the pulses of the multivibrator, the charges on the capacitors 14 and 15 are insufficient to unlock the transistor 10 and the current through the transistor 10 of the dynamic element 9 is minimal - "O (Fig. 2). With an increase in the amplitude Um of the pulses and the achievement of the value Um Um (Fig. 2), transistor 10 instantaneously opens and the current through the transistor 10 abruptly changes from the minimum value at point 17 to the maximum at point 18. A further increase in Um causes a slight and smooth change in current transistor 9.

When the amplitude Um of the pulses decreases, the switching on of the transistor 9 occurs at a lower amplitude value (Fig. 2). The process of turning off the transistor 10 is an avalanche-like process, and the magnitude of the current J abruptly varies from the value at point 19 to the minimum value at point 20. Thus, the dynamic element 9 has an S-shaped hysteresis characteristic and it can work in

5 two stable states: "1 (on) and" O (off).

To switch a dynamic element from one steady state to another, the operating point on the S-shaped characteristic (Fig. 2) is selected within the interval Um-Um, i.e. at the point Um. In this case, in the initial state (when the symmetric multivibrator is turned on), the transistor 10 is turned off and, accordingly, the internal resistance of the dynamic element is maximum and the pulse repetition frequency of the multivibrator is minimal (Fig. 3, pulses 21). This state is stable, it is maintained for an arbitrarily long time, until it is affected by the governor.

0 pulse U.

When exposed to the control pulse Ui, the transistor 10 opens and the current through it abruptly changes from the minimum value at the point Ui to the maximum (Fig. 2), which dramatically changes the internal resistance of the dynamic element 9. The change in the internal resistance of the dynamic element changes the parameters circuits of a symmetric multivibrator and the pulse repetition rate increases sharply (Fig. 3, pulses 22). This state is stable, and it persists even after the termination of the control pulse Ui.

To switch the multivibrator back to a low pulse repetition rate, the control pulse U2 of negative polarity is applied. In this case, the transistor 10 is turned off, and the internal resistance of the dynamic element 9 takes the maximum value, and the pulse repetition frequency of the multivibrator decreases to the initial value (Fig. 3, pulses 23). This state is also stable, it is maintained for an arbitrarily long time, i.e. until the next impact by a pulse Ui.

The resistance value of the resistor 16 is several tens of kilo and serves to select the operating point of the dynamic element.

In known devices, it is not possible to change the pulse frequency by supplying a single control pulse. In the invention, the pulse repetition rate is changed by applying a single control pulse, which is advantageous for remote and other control options. Thus, the device has two stable states in terms of pulse frequency. In this case, the pulse repetition rate changes 2.5 times.

Claims (1)

CONTROLLED MULTIVIBRATOR containing a symmetric multivibrator with collector-base connections, a transistor with a conductivity type similar to multivibrator transistors, a resistor, a first diode, a first capacitor and a first control signal source, characterized in that, in order to control the multivibrator frequency by changing the time resistance circuit, it introduced the second and third diodes, the second capacitor, the second source of the control signal, while the base of the transistor through a resistor is connected to a common bus and the anode of the first diode, the transistor collector through a first capacitor connected to the common bus, the emitter via a second capacitor is connected to the collector of symmetrical multivibrator, and the cathodes of the first and second diodes and the anode of the third diode, the anode of the second diode and the cathode of the third respectively _to but connected to the first and a second source of control signals. n {X — ® ^{; 7r} K - Thi, with joint venture to