SU1005274A1 - Pulse generator - Google Patents

Description

The invention relates to a pulse technique.

Known generator pulses, containing an operational amplifier, a resistive divider, a field-effect transistor, capacitors and a resistor C is the device's disadvantage. is the use of three sources of stress;

The most important technical entity to the proposed device is a multivibrator containing two transistors of different types of conduct, a capacitor, a diode, resistors, two additional transistors, two control current sources, a matching device 2.

The disadvantages of this device are its complexity, as a result, low reliability, the need to use two additional sources of control current and low reliability. In addition, the device has a low speed due to the considerable duration, the front and the cutoff of pulses and insufficient functional possibilities, since it is impossible to separately adjust the duration and pause between pulses.

The aim of the invention is to enable a pulse generator, to ensure separate adjustment of the pulse duration and the time between pulses, as well as to reduce the length of the front and the cutoff of the pulse. The goal is achieved in a device containing a resistor that is emitter follower

10 RC circuit and voltage divider in the emitter circuit of the emitter follower, as well as the first and second transistors of different conductivity types, the emitters of which are connected by themselves, and the collector of the second of them is connected to the emitter follower input and to the first output of the resistor, the base of the first transistor is connected to the junction point of the capacitor and resistor

20 of the serial RC circuit, and the base of the second transistor is connected to the connection point of the voltage divider resistors. In this case, the collector of the first transistor is connected to the power bus,

25 and the second pin of the resistor. Connected to the common bus.

The drawing shows a schematic diagram of the device.

 The pulse generator contains emit30 true follower 1, a series RC circuit of resistor 2 and capacitor 3, a voltage divider on resistors 4 and 5, the first and second transistors n-pm and pnp types 6 and 7, resistor 8 .

A voltage divider on resistors 4 and 5 is included in the emitter circuit of the emitter follower 1, the emitters of the first and second transistors are combined, the collector of the first transistor is connected to the power bus, its base to the midpoint of the RC circuit 2 and 3, the collector of the second transistor is connected to the emitter input the repeater, the first output of the resistor 8, the second output 9 of which is connected to the common bus.

The device works as follows.

At the first moment after switching on, at the input of the emitter follower 1 a zero potential is established. In this case, the transistor 6 is closed, and the base of transistor 7 is set to the voltage, which is determined by the ratio of the voltage divider resistors on the resistors 4, 5 and is transmitted to the emitters, respectively, of the transistors 6 and 7. The charge of the capacitor 3 starts through the resistor 2 included in the base of the closed transistor 6. At the moment when the charge voltage in the base of the triisistor b becomes the voltage of the emitter, the transistors 6, 7 open, and the transistor 1 closes. At output 9, a positive pulse appears, the duration of which corresponds to the discharge time of capacitor 3 through the base-emitter transitions of transistors b and 7, which are kept by the discharge current in the open state.

After the discharge of the capacitor 3 to the level at which the transistor 7 is closed, the transistor opens, which leads to the closing of the transistors b. Next, a pause between the pulses is formed, the duration of which corresponds to the charging time of the capacitor 3 through the resistor 2 to the threshold voltage, the level of which is set by the divider on the resistors 4 and 5.

The time between pulses can be adjusted by varying the resistance of resistor 2. In this case, the pulse duration does not change, since the time constant of the discharge circuit of capacitor 3 remains unchanged.

The pulse width is controlled by changing the resistances of the rheistors 4 and 5, which simultaneously leads to a change in the frequency of the next, since the voltage threshold to which the capacitor 3 is charged is changed. Thus, in the device, it is possible to independently adjust the tracking frequency and the time between pulses and duty cycle. In this case, there is the possibility of both preserving the duty cycle of the pulses with a change in frequency, and a change in the duty cycle at the same frequency. In addition, in the proposed device provides a reduction

of the pulse front (in the opening order of the transistors 6 and 7) due to the action of the accelerating feedback from the emitter of the transistor b, included

io emitter follower circuit, through transistor 7, which is included According to the amplifier circuit with a common base, through emitter follower 1 and capacitor 3 to the base of the transistor b.

The cutoff duration of the pulse (at the time of closing of the transistors b, 7) is reduced due to the counter current of the discharge current of the capacitor 3 through the base of the emitter of the transistors b, 7 and due to the same accelerating positive feedback from the emitter of the transistor b to its base.

Claims (2)

1. USSR author's certificate № 750702j cl. B 03 K 3/281, 04.17.78, 0 2. USSR author's certificate number 566314, cl. H 03 K 3/281, 25.12.74. five 0