SU516180A1 - Self-excited multivibrator - Google Patents

Description

one

The invention relates to electric pulse generation devices and can be used in the pulse technique and in various automation and telemechanics devices.

A self-excited multivibrator on transistors of the same conductivity type with collector-base connections is known, between the collectors of transistors of which are connected two series-connected circuits containing a control transistor and a capacitor.

However, the scheme of such a multivibrator is complex and it affects the effect of the control transistor on the time of the driving circuit, which leads to instability of the parameters of the generated pulses.

The purpose of the invention is to eliminate the influence of the control transistor on the time parameters of the driving circuit.

The goal is achieved due to the fact that the control transistor is made on a triode of the opposite conductivity type, the base of the control transistor is connected via a common bus capacitor, directly to the connection point of the series-connected resistors, the collector is connected to the common bus the point of the divider formed by one of the time-setting resistors of the multivibrator.

FIG. 1 shows a circuit diagram of a self-initiating multi-moderator; ) ia FIG. 2 are graphs of voltages appearing on the resistor of the time of the driving circuit during operation of the multivibrator.

The proposed multivibrator circuit consists of transistors 1 and 2 of the pnp type, the collector loads of which are resistors 3 and 4, and the capacitances of the capacitors 5 and 6. The resistance of one of the driving time of the multivibrator is resistor 7, and the other resistance is made in the form of a divider with resistors 8 and 9, to the midpoint of which is connected the emitter of the control transistor 10 of the type “p- / g-p. The control transistor 10 is connected according to the emitter follower circuit, the load of which is resistor 8, and the voltage comes to the base from the midpoint of the divider made on resistors And 12, connecting the collectors of transistors 1 and 2. The capacitor 13 is designed to smooth the voltage pulsations arising from the base of the transistor 10 at the moment the multivibrator is switched from one state to another.

Scheme.ma works as follows.

If when switching on the power supply or during the operation of the multivibrator, both transistors 1 and 2 turn into saturation, then the voltages on their collectors b are close to zero. Consequently, the voltage at the base of the emitter follower made on the transistor 10 will also be close to zero. The control transistor 10 will open a voltage across its transmitter at point 14 will repeat the voltage at its base. This will lead to the exit of the saturation mode of transistor 1, which will inevitably cause the onset of a self-oscillating process. When the multivibrator goes into self-oscillatory mode of operation, the voltage on one of the collectors of transistors 1 or 2 will be close to the voltage source of the tapes. Consequently, the voltage at the base of the transistor 10 will be about half the voltage of the power source. The parameters of the voltage divider, made on the resistors 8 and 9, are selected in such a way that the voltage on the emitter of the transistor 10 remains always less than on its base. Therefore, when the multivibrator enters the auto-oscillation mode of Root, the transistor 10 closes and does not affect the time parameters of the driving circuit.

In order to clarify the principle of operation of the control transistor, we consider the graphs of the devices presented in FIG. 2, where the values of co-resistance of resistors 9 and and, but, but the ordinate axis, the distribution of the voltages on these resistors beyond the ground at different moments of the multivibrator operation, are plotted on the abscissa axis. Moreover, the beginning of resistor 9 is marked by point 15, the end of resistor Y and 1 are each of resistor b by point 14, and the end of resistor b by point ID, as well as ka fig. 1. Direct i / refers to the case when transistor 1 is in saturation mode, and ir ib is when transient i has just closed, due to the onset of the discharge of capacitor o. As the capacitor is discharged (3 voltages across the resistors B and Y are also distributed by the latency, which should occupy the intermediate position between forward 1 / and Ib. To maximize the fuzziness in the same Fig. 2, the pan-wires are shown at the base of the transistor 10. When M) the ltier generator does not generate (transistors 1 and 2 are in the passive mode) the incidence at the oasis of the transistor 10 is close to zero, which practically coincides with the x-axis. When the multivibrator operates in a self-oscillating mode, the equipments based on the 1U transistor are about nojiOBHHbi and power source wiring, which is denoted forward 19. In the process of autowheel in the multivibrator, the voltage and base of the transistor 10 increases from zero to the value noted by the direct voltage nineteen.

From a consideration of the stress graphs shown in FIG. 2, it follows that the choice of the ratio between the resistors 9 and 8 has a substantial value for the operation of the multivibrator. If the emitter of transistor 10 is connected to point 15 (resistor 9

equal to zero), then the transistor 10 may not cause the start of self-oscillations, since, for example, at its base and the emitter will be approximately one point. If we take the value of resistive resistor 9 to be larger than pm of resistor 8, then during the operation of the multivibrator in self-oscillating mode, the emitter voltage of the transistor 10 (right 17) will exceed the voltage at its base (right 19),

the transistor 10 will open and influence the timing parameters of the driving circuit.

Therefore, so that the transistor 10 effectively enough caused the onset of the self-oscillating process in the multivibrator while

the same time influenced the parameters of its driver circuit time, the magnitude of the resistor 9 should be chosen to the left of the intersection point of the visible 17 and 19. For example, if among the point 14 the divider is selected as indicated by

FIG. 2, then at the moment the multivibrator is turned on, strained close to the bullet at its base, the voltage at the emitter has a full, indicated by point 20, transistor 10 opens and causes oscillations to occur. When the transistor enters the self-oscillating mode, the voltage at its base will increase to the value indicated by the D 19, and on the emitter it will change from the value indicated by the point 21 to the value indicated by

point 20. Therefore, when the multivibrator operates in the self-oscillating mode, the transistor 10 will be locked and will not affect the parameters of the time of the driving circuit. The efficiency of the emitter newtor is ensured by the fact that its load resistance is only a fraction of the resistance of one of the time of the driving circuits of the multivibrator. It also eliminates the effect of the control transistor on

parameters of the master circuit of the multivibrator.

F o rm u l a n 3 o b r e s t u u

A self-excited multivibrator on transistors of the same type of conduction with a collector base connection, whose collectors of transistors include two series-connected resistors containing a control transistor and a capacitor, characterized in that, in order to eliminate the effect of the control transistor on the time parameters The control transistor circuit is made on a triode of anti-reverse conductance, and the base of the control transistor is connected via a common bus capacitor, respectively Primarily - with the point of connection of these series-connected resistors; the collector is connected to the common bus;

-f, 4

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