SU1714790A1 - One-shot multivibrator - Google Patents

Abstract

The invention relates to a pulse technique and can be used in precision frequency-voltage (current) measuring transducers, timers. The aim of the invention is to increase the stability of the duration of the formed pulse. The goal is achieved by comparing the part of the total voltage drop caused by the current of the source 1 on the series-connected driver of the capacitor 2 and the reference resistor 4 allocated by the voltage follower 7 vi by the voltage divider 8, with the voltage decreasing on the reference resistor 4.1 or .

Description

The invention relates to a pulse technique and can be used in precision measuring converters frequency-voltage (current), timers IT.D., .- ,. , .V /

Known waiting multivibrator containing two transistors, time specifying a capacitor and a resistor {see And, P. Stepanenko. Fundamentals of the theory of transistors and transistor circuits. Energie, M., 1967–616c.J;

The MEASUREMENT of such a multivibretor is the low stability of the pulse duration and a significant recovery time;

Also known is a standby multivibrator, which contains a trigger on transistors of a different type of conductivity, a time setting capacitor, a charge current source, a time setting capacitor, a siren | comparator, and a dissipating diode in the discharge time circuit.

the condenser (see. AS USSR. N: 454671, CL.-H 03 K 3/284, 08.16.82)

The disadvantage of this multivibrator should be attributed to the low temperature stability of the duration of the generated pulse, the value of which is difficult to predict and calculate. To achieve high temperature stability, it is necessary to introduce individual corrective adjustments into the multivibrator circuit. This is accomplished by temperature testing. It should also be noted that even after individual adjustment of each multivibrator, it is not possible to ensure long-term stability of duration due to aging of the elements.

The closest to the proposed technical essence and the achieved result is a standby multivibrator (AS USSR 1290494. CL. H 03 K 3/284, 1985) containing a trigger on transistors of different types of conductivity, the current source loaded on the series-connected the reference resistor and the time setting the capacitor, a switch key, the time setting co-capacitor, connected in parallel to the plates of the latter, the differential amplifier whose inputs are connected to the terminals of the reference resistor and a comparator, the first input of which is connected to water soedyn yuschemu reference resistor and capacitor defining the time, and the second - to the output of the differential amplifier-Hoc.

The specified standby multivibrator has an increased stability of the pulse duration due to the use of a single current source both for charging the time of the driving capacitor and for creating the reference voltage. However, a differential amplifier separating the reference voltage (voltage drop on the reference resistor) from the sum of voltages (on the reference resistor and the time of the driving capacitor), introduces both the error (in the selection of the reference voltage) and the instability when the external conditions change (changes e mapr:, power supply, aging of the feedback elements of the amplifier, etc.) restrains the further increase in the long-term stability and invariance of the duration of the formed pulse.

The goal of the inventor is to further increase the stability of the pulse duration when the external conditions change and the elements are aging.

The goal is achieved by the fact that in a multivibrator with a holding trigger, the first inputs of which the output is respectively the device input and output, the current source, the time setting the capacitor, the first plate connected to the current source output, the reference resistor is first connected to the second capacitor plate, and the second - to the common power bus, the key of the discharge is the time of the driving capacitor, the input connected to the second output of the trigger, and the output is parallel to the plates the time of the driving capacitor, comparator, output Secondly, it is connected to the second input of the trigger; according to the invention, a voltage follower is added to it - the input of which is connected to the first capacitor plate and the voltage divider - the input of which is connected to the output of the voltage follower, and the output to the first input of the comparator. the first pin of the reference resistor,

The set of essential features of the distinctive part of the claims of the invention of the claimed device in the prior art was not found, therefore, the claimed device meets the criterion of the significance of differences.

The drawing shows a diagram of the proposed standby multivibrator.

The proposed multivibrator contains the source current 1 (see, for example, P. Horowitz, W. Hill, Art of Circuit Engineering, Volume 1, Mir, M., 1983, Fig. 3. 11, m / s 140 UD17, output transistor KA 304A), time setting capacitor 2,

switch 3 (m / s 564KTZ) capacitor discharge 2, reference resistor 4, comparator 5 (m / s 521 САЗ), trigger 6 (m / s 564 ТМ2) the first input and output of which are the device input and output, repeater

7 (m / s 14d UD 17) voltage and resistive divider 8.

The proposed standby multivibrator works as follows.

In the initial state, the trigger b occupies the state in which the low-level signal acts on its first output and the high state on the second output. The switching pins (X) of the key 3 are in the closed state, since

its control input (V) is a high level signal. The current () of the current source 1 is closed through the closed terminals (X) of the switch 3 and the resistor 4. The voltage drop Ua on the plates

the capacitor 2 is determined by the expression Ra (where Kz is the resistance of the key 3 in the trailed state). The voltage drop across the resistor 4 on the terminal etc by the expression. Voltage U4 is

reference for comparator 5 and acts on its B1; the entrance is.

The total voltage drop (on the shorted capacitor 2 plates and the resistor 4) through the voltage follower 7 is fed to the input of the resistor divider 8 voltage. From the output of the divider 8, the part of the voltage Uc is fed to the first input of the comparator 5. The value of the voltage acting on

the first input of the comparator 5 is determined

U8 --iT (A® division ratio

1 divider 8, K factor is selected from

conditions U4 „

When a pulsed pulse arrives at the input of the multivibrator, trigger 6 changes its state. A high logic signal arises at the first output.

Claims (1)

10 claims A waiting multivibrator containing a trigger, the first input and output of which is the input and output of the device, current source, time-consuming capacitor, 15 is the first plate connected to the output of the current source, the reference resistor is connected to the second plate of the capacitor by the first and the second to the common power bus, a capacitor discharge key, the input connected to the second output of the trigger, and the output parallel to the capacitor plates, the comparator whose output is connected to the second input of the trigger, about τη and especially with the aim that 25 to increase the stability of the duration of the generated pulse, a voltage follower is additionally introduced into it, the input of which is connected to the first capacitor plate and the voltage divider, input 30 of which is connected to the output of the voltage follower, and the output to the first input of the comparator, and its second input is connected to the first output reference resistor.