SU443463A1 - Pulse generator - Google Patents

Description

one

The invention relates to a pulse technique and can be used as a clock pulse generator.

A pulse generator is known which contains an avalanche transistor with a resistor in the collector circuit and the base circuit, a dc amplifier, and a storage capacitor in the feedback circuit of the amplifier.

However, to obtain a low frequency for such a generator, it is necessary to increase the gain of the amplifier, which complicates it.

In order to increase the amplitude and period of the generated oscillations in the proposed generator, a dynistor is connected to the emitter circuit of the avalanche transistor, and a chain of a series-connected capacitor and a resistor, which is bridged by a diode, is connected to the circuit of its base.

FIG. 1 shows the basic electrical circuit of the proposed generator; in fig. 2 - a family of current-voltage characteristics of the avalanche transistor, which explains the operation of the generator.

The proposed generator contains an avalanche transistor 1, in the emitter circuit of which a distor 2 is connected, connected by a collector through a resistor 3 to a power source 4. A capacitor 5 is accumulative, and a load 6 is connected in series with it.

Resistor 7, capacitor 8, diode 9 determine the open state time of transistor 1. Resistor 10 connects the base of the transistor to a common circuit bus.

FIG. 2 the following notation is accepted: I, II, III - the current-voltage characteristic of the transistor in the normal mode and IV - in the avalanche mode; 1 / Кз - static load line; UM - avalanche breakdown voltage

transistor in a circuit with a torn emitter; UZ - voltage across the transistor in a circuit with a broken base.

The generator works as follows. The total oscillation period of the generator consists of two stages.

At the first stage the avalanche transistor is closed. The voltage on its collector initially after switching on the power source 4 varies in accordance with the charge of the capacitor 5 from the voltage source 4 through the resistor 3 and the load 6. At the moment t / m is reached on the capacitor 5, the collector junction of the transistor 1 is punched. The charge of the capacitor 8 starts from

power supply 4 through diode 9, the transition

collector-base of the transistor, resistor 3 (on

stages of charge of the condenser 8 collector

the transistor period is similar to a stabilitron).

A charge of capacitors 8 and 5 is terminated,

when the voltage on the capacitor 8 reaches the turn-on voltage f / on of the dynistor 2, the voltage drops across it, and the base of the transistor 1 through the resistor 7 is applied a negative voltage of the capacitor 8. In connection with this, the transistor 1 enters the saturation and the second stage of forming the oscillation period of the circuit begins.

Since the residual voltage across the transistor 1 and dynistor 2 is much less than LM and t / on, respectively, the pulse amplitude

 + on

The open state of transistor 1 is determined by the discharge current of the capacitor 8. Its discharge passes through the circuit: resistor 7 - base-emitter junction of transistor 1 - distor 2. At some boundary current base

Jjl

bgr b «s

(B is the transmission coefficient of the base current of the transistor in the normal mode) transistor 1 goes out of saturation (position I, fig. 2), after which it starts to work in active mode (position II, P1, fig. 2). As the base current of the transistor 1 decreases, its volt-ampere characteristic changes position, and its operating point moves along the load line (Fig. 2) from position I, II to position III.

In position III, the base current of the transistor is zero. The dynistor 2 in this position of the avalanche transistor operating point with correctly selected circuit parameters must remain in the open state, i.e. its cut-off current must be less

four

Un-U R,

Transistor 1 is turned off at the time of changing the sign of the base current, i.e., the base current becomes negative, and the volt characteristic of transistor 1 is in position IV (Fig. 2). The operating point from position III passes

0 in position IV, characterized by high resistance, i.e., mashing of an avalanche transistor occurs. A decrease in the current through the transistor also leads to the locking of the dynistor 2. This completes the second

5 stage formation period. The circuit returns to its original state, in which the avalanche transistor 1 and dynistor 2 are turned off, the capacitor 8 is discharged, and the capacitor 5 is charged before the voltage U.

Further, the processes in the circuit are repeated. The magnitude of the capacitor 8 or resistor 7, you can adjust the oscillation period of the circuit within wide limits.

c) invention

A pulse generator containing an avalanche transistor with a resistor and a storage capacitor in the collector circuit and a base resistor, characterized by

0 by the fact that, in order to increase the period of the generated oscillations and the amplitude of the output pulses, a dynistor is inserted into the emitter circuit of the avalanche transistor, and a chain of a series-connected capacitor and a resistor triggered by a diode is inserted into the base circuit.