SU476671A1 - Sawtooth generator - Google Patents

Description

one

The invention relates to a pulse technique.

A sawtooth generator is known, which contains a differential transistor amplifier with a current stabilizing transistor in the emitter circuit, the time specifying a capacitor. A disadvantage of the known generator is the insufficient duration of the output pulse. The aim of the invention is to increase the duration of the output pulse.

In the described generator, this goal is achieved by including the time of the driving capacitor between the collector circuit of one transistor and the base of the other.

A schematic diagram of the described generator is shown in the drawing.

The generator contains a differential amplifier with transistors 1, 2, resistor 3, included in the collector circuit of transistor 1, current stabilizing transistor 4, ap & rear, capacitor 5, diodes 6, 7, resistors 8-10, power sources 11, 12.

The generator works as follows.

Transistors 1 and 2 of the differential amplifier operate in a key mode, alternately opening and closing. With the closed transistor. 1 and an open transistor 2, the charge of the capacitor 5 is small and unchanged in magnitude by the base current of the transistor 4. As the charge progresses, the voltage on the capacitor 5 increases linearly, and at the base of the transistor 2 decreases linearly, and the diode 7 is kept closed ( this

corresponds to the straight stroke of the saw). At this time, the voltage at the base of the transistor 1 relative to the common point of the power sources is zero, since the transistor 1 is closed and no current flows through its base diode 6.

When the voltage at the base of transistor 2 decreases, transistor 2 begins to close, and transistor 1 opens. Due to the positive feedback, an avalanche-like tipping process occurs, as a result of which the transistor 1 opens completely and the transistor 2 closes and the discharge of the capacitor 5 starts through the circuit: the collector of the transistor 1, the current source at the transistor 4, the power source 12 and the open diode 7 In order to accelerate the process of discharge, corresponding to the process of restoring the circuit, and also in order to make the most complete use of the voltage of the power source I, it is necessary that in this case the transistor 1

was in a saturated state. Since the discharge current (collector) significantly exceeds the charge current (base) of the capacitor 5, the recovery time is much less than the forward stroke of the saw. As far as

the capacitor voltage between the bases of the transistors 1 and 2 decreases (in absolute value) and the process of reverse avalanche-like tilting occurs, after which the capacitor 5 starts charging again.

Diodes 6 and 7 of the same type. The use of diode 6 contributes to the steady self-excitation of the generator.

The amplitude of the output sawtooth pulses corresponding to the forward stroke when the circuit is operating with the saturation of transistor 1 is approximately equal to the voltage of the power supply 11. If there is no saturation, then the amplitude of these pulses does not depend on the voltage of the source 11, generated by the flow of the collector current of the transistor 1, reduced by the amount of voltage on the open diode 7. The amplitude of the negative pulses, having an approximately rectangular shape and corresponding to the process of tanovlenii equal voltage drop on the diode 7 open.

The saw angle depends on the collector current of transistor 4, the current gain of transistor 2 and the capacitance of capacitor 5.

To reduce the recovery time, capacitor 5 should be connected to the collector of transistor 1 via an emitter follower (not shown). In this case, the recovery time may be a few percent of the forward stroke time.

The generator can also work in the inhibited mode. To do this, a small bias voltage must be applied to the base of transistor 1, which, when the generator starts up, must be compensated for by short clock pulses.

The nonlinearity coefficient of the generated sawtooth pulses is smaller, the greater the value of the resistance of the load connected to the generator.

Subject invention

A sawtooth generator containing a differential transistor amplifier, in the emitter circuit of transistors of which a stabilizing transistor is connected, and the bases through diodes are connected to a common point of the generator, and the time specifies a capacitor, characterized in that, in order to increase the duration of output pulses, the time specifying a capacitor is turned on between the collector of one of the transistors of the differential amplifier and the base of the other.

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