SU756607A1 - Multivibrator - Google Patents

Description

The invention relates to the field of pulsed and computing equipment and can be used in various devices. In particular use can be multivibrator kont- ³ ROLL-testing apparatus as the master clock.

Multivibrators are known that are implemented on the basis of two-layer distributed ..NS structures with electron frequency tuning 1.5–2 · times [1].

However, a slight frequency tuning of such multivibrators, as well as the use in them of elements “made by different technologies, are obvious shortcomings.

2C

Known multivibrators containing serially connected logical elements of transistor-transistor logic, one of which is timed by a capacitive capacitor [2].

The disadvantage of such multivibrators is the lack of a smooth frequency adjustment of the pulse pic. Consequently, in a wide range.

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The invention is secu ⁴ chenie smooth frequency control.

To achieve this goal, a multivibrator containing series-connected logic elements of transistor-transistor logic, one of which is timed-capacitor-inserted, has a potentiometer and an expander valve, and one potentiometer is connected to the collector expansion input by an OR capacitor-bypass element another conclusion - to the collector outlet of the valve - expander, the emitter output of which is connected to the common bus, and the input to the input is logical an element connected in front of a logic element shunted by a time-dependent capacitor.

FIG. Figure 1 shows the functional scheme of the multivibrator; in fig. 2 diagram of the voltage of the multivibrator, the left part of which refers to the generated pulse sequence with the maximum frequency, and the right part to the sequence of the pulses with the minimum frequency.

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756607

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The multivibrator contains five series-connected logic elements 1–5. Logic элемент element 3 is shunted by a time-sensitive capacitor 6. A potentiometer 8 is connected to the collector input 7 of the logic element 3, intended for expansion by OR, the other end of which is connected to the collector output 9 of the valve -expander 10. The emitter output 11 of the latter is connected to the common power supply bus, and the input 12 - to the output of the logic element 1.

The logic element 3 contains a resistor 13 connected to the collector of the transistor 14, a resistor 15 connected to the base of the multi-emitter transistor 16, and a transistor 17 whose collector is connected to the input of the logic element 4. The expander valve 10 contains a transistor 18,

^ The mitter of which is connected to the general Shi-20 not of the power supply, but the collector - to the potentiometer 8.

Multivibrator works as follows.

Let at the considered time moment-25 meni (Fig. 2) the potentials at the points α, b, and с are low. The voltage at point c increases exponentially with a time constant determined by the charge circuit of capacitor 6. here

The charge current of the output capacitor 6 is formed from the output current of the logic element 3 flowing through the circuit: + - resistor 13 - transistor 14 - time-sensitive capacitor 35 6, etc., and flowing input current of the logic element 4. Upon reaching the threshold of operation E then ( Fig. 2, a) of a logic element 4 (moment of time) at its output dd and at the input of logic element 5 a voltage drop appears from a high level to a low, as a result a voltage drop appears at point σ at the input of logic element 1 and at point b low level to a height _e okay The voltage drop at point b is equal to E _then . This voltage drop through the time-keeping capacitor b is transmitted to the point c, the potential of which rises to a value of 2 Ε _{ηορ. The} process of recharging the time-dropping capacitor begins.

Almost all current flowing through resistor 15 and the base-emitter junction of a multi-emitter transistor 55

16, flows into the time capacitor and the transistor 17. At the point

with a decrease in voltage

to the threshold of logical

element 4 and the circuit returns to

initial state (moment

time ί _a ).

In the time interval ί! -1 _g , when the input of the expander valve 10 is high and the transistor 18 ^ is open, when the resistance of potentiometer 8 changes, the internal resistance of transistor 14 changes, and consequently, the charging current of the time-canceling capacitor 6 changes.

In the time interval 1 ₂ -ί ₃ at the input of the expander valve, the low level is set, the transistor 18 is closed and the change in resistance of the potentiometer 8 has almost no effect on the operation of the circuit.

Due to the introduction of a potentiometer and an expander valve into the multivibrator, by varying the resistance value of the potentiometer, a gradual frequency tuning of the generated pulses is ten or more times with the selected capacitance value of the time-dropping capacitor, while the pulse duration remains almost constant.

Claims (1)

Claim A multivibrator containing transistor-transistor logic connected in series, one of which is shunted by a time-sensitive capacitor, which, in order to ensure a smooth frequency control, a potentiometer and an expander valve are inserted into it, and the potentiometer is connected to the expansion manifold input on the OR of the logic element, shunted by the time-conducting capacitor, and the other output to the collector output of the expander valve, whose emitter output is one with the common bus, and input - to the input of NAND gate, AND gate connected upstream, eashuntirovannym timing capacitor.