SU1003306A1 - Multivibrator - Google Patents

Description

The invention is intended for use in instrumentation engineering.

Photosensors of multivibrators with collector-base feedbacks li are known.

A disadvantage of devices of this type is the limited frequency overlap range per frequency or duty cycle of generating pulses, and the thermal stability of the circuit is low.

The closest technical solution to the proposed one is a multivibrator with an inter-emitter capacitor collector and two emitter resistors, emitter and ocHOBHbiM power sources 2j.

A disadvantage of the known device is also a limited range of frequency overlap or duty cycle of the generated pulses, the thermal stability of the circuit is low when a resistor is switched on in the zmitter power supply circuit.

The purpose of the invention is to expand the frequency range overlap in frequency and increase thermal stability.

The goal is achieved by the fact that in a multivibrator containing a common bus, first and second power buses, first and second transistors, a collector resistor, the first and second emitter resistors, the first capacitor, in which the emitter of the first transistor is connected to

10 to the first power bus and through the first capacitor to the emitter of the second transistor, the base. Connected to the common bus, the emitter of the second transistor through the second elitter resistor

15 -Godklyuchen to the common bus, the collector directly, and the base through the collector resistor connected to the second power bus, additionally introduced the third transistor, the second

20 a capacitor and a zener diode, with the cathode of the zener diode connected to the collector of the first transistor, and the anode to the base of the second transistor, the base of the third transistor connected to

25 to the emitter of the first transistor, the collector to the second power supply bus, and the emitter through the second capacitor connected to the emitter of the second transistor.

As the first emitter

Claims (2)

30 resistor photoresistor used. The drawing shows the scheme of the multivibrator. The multivibrator contains a common bus 1, the first and second power buses 2 and 3, the first and second transistors 4 and 5, the collector resistor 6, the first and second emitter resistors 7 and 8, the first capacitor 9, the second capacitor 10, the third transistor 11, a zener diode 12. The device operates as follows. When capacitor 9 is charged, transistors 4 and 11 are closed, and transistor 5 is open. Capacitor 9 is charged through the first emitter resistor 7. Transistor 4 is locked when charging capacitor 9 due to the fact that its emitter has a large negative potential, which consistently decreases as the capacitor 9 charges. The base has a positive potential. Transistor 4 opens at the moment when its emitter potential reaches zero. Capacitor 9 begins to discharge through the opened emitter junction of transistor 4, which leads to its saturation and locking of transistor 5. When transistor 4 is unlocked, transistor 11 opens, both capacitors of capacitor 10 The capacitors 9 and 10 are discharged through the second emitter resistor 8, ensuring the locking of the transistor 5. The unlocking of the transistor 5 occurs at the moment when the stabilizing voltage of the Zener diode 12 and the W emitter on the resistor 8. The presence of Zener diode 12 provides for fast switching of the circuit, after which the capacitor 9 starts charging again. Using the photoresistor and Zener diode 12 as the first emitter resistor allows expanding the range of conversion of the luminous flux into the frequency or duty cycle of the generated pulses. In addition, the introduction of the Zener diode allows thermally stabilizing the circuit by unlocking the transistor 5, since the Zener diode and the transistor have similar temperature coefficients with opposite signs. The introduction of an additional transistor 11 and an additional capacitor 10 prevents the reverse current of the locked transistor from affecting the thermally stable one, since this circuit is a current consumer from the capacitor 9. With the same type of transistors 4 and 11, their reverse currents are quite close, therefore, it can be considered that compensation occurs the current of the locked emitter junction of the transistor 4 to the charge rate of the capacitor 9. Formula of the invention 1. A multivibrator containing a common bus, first and second power buses, first and second tr anisistor, collector resistor, the first and second emitter resistors, the first capacitor, the emitter of the first transistor through the first emitter resistor connected to the first power supply and through the first capacitor to the emitter of the second transistor, the base is connected to a common bus, the emitter of the second transistor through the second emitter resistor is connected to common busbar, the collector directly, and the base through the collector resistor is connected to the second power bus, characterized in that, in order to increase its thermal stability and expand part In this range, a third transistor, a second capacitor and a zener diode are additionally introduced, the cathode of the Zener diode is connected to the collector of the first transistor, and the anode to the base of the second transistor, the base of the third transistor is connected to the emitter of the first transistor, the collector to the second capacitor is connected to the emitter of the second transistor. 2. Multivibrator according to claim 1, characterized in that, in order to provide frequency tuning by the light flux, a photoresistor is used as the first emitter resistor. Sources of information taken into account in the examination 1.Budenov V.P. Relaxation generator-pulse converters of non-electric quantities. M., Energie, 1974, p. 108 2. Yakovlev V.N. Handbook of pulse technology. Kiev, Technique 1974, p. 205.