SU446944A1 - Threshold device - Google Patents

Description

one

The invention relates to the field of pulsed technology. The device can be used as a discriminator of the amplitude of the pulse signals, when the reproducibility of the duration of these signals is strict.

Known threshold devices that form time intervals equal to the duration of the pulse signals acting on the device, made according to the Schmitt trigger scheme. The duration of the output pulse of such devices in cases of a distorted input signal does not correspond to the duration of the latter, and in the case of oscillations of an oscillatory nature, several pulses can be formed at the output of such devices when exposed to a single pulse.

The purpose of the invention is to increase the noise immunity of the device. This is achieved by introducing an additional Schmitt trigger into the device, connecting the input to the input signal bus, and output to one of the AND inputs connected by another input to the Schmitt trigger output, and output to one of the OR inputs, the other input of which connected to the input bus and the output to the Schmitt trigger input.

FIG. Figure 1 shows the functional scheme of the proposed threshold device; on

2

FIG. 2 and 3 are graphs of operating signals.

The device contains a Schmitt trigger 1, an OR 2 circuit, the first input of which is connected to the input signal bus, and an output to the input of the aforementioned Schmitt trigger, an AND 3 circuit, connected by a first input to the Schmitt trigger output, and an output to the second input of the circuit OR, n auxiliary Schmitt trigger 4, connected by an input to the input signal, and an output to the second input of the “I.

The input impulse signal (/ i is fed to the first input of the circuit OR 2 n to the input of the auxiliary Schmitt trigger 4. Irn value f / больш is greater than the trigger threshold of the auxiliary Schmntt trungger U, but less than the trigger threshold of the Schmitt trigger 1 f / m, the auxiliary trigger Schmitt and at its output appears impulse 1/3, which is fed to the input circuit "I.

Upon reaching the input signal f / j level t / ni. determining the triggering threshold of the entire device, the Schmitt trigger I is triggered via the ILR1 2 circuit. The impulse of this trigger goes to the other input of the “AND 3” circuit. Since the pulses are present at both inputs of the “AND” circuit, the latter generates a pulse t / 2, which arrives at the output of the device and the second input of the “OR” circuit. The C / g impulse through the OR circuit is fed to the input of a Schmitt trigger 1 and duplicates the effect on the last input signal. Thus, pulse 1/2 is for trigger 1 a positive feedback signal. If, after triggering trigger I, the level of the top of the input pulse / 1 falls below the level, but remains above the level U "., The pulse from the output of the device is not interrupted, since pulses are not interrupted at the inputs of the" I. When the pulse level Ui becomes less & Un, the auxiliary Schmitt trigger is locked. The impulse (3) is terminated and the conditions for the formation of an impulse (a) are broken by the " i'm broken, the impulse 1/2 is terminated. The Schmitt trigger 1 is locked.

Thus, the proposed threshold device generates a pulse Uz, the duration of which is determined by the duration of the pulse and does not depend on the distortions of the peak of this pulse.

Vyaz

fuz1

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Subject invention

Threshold device based on a Schmitt trigger, characterized in that, in order to improve noise immunity, an additional Schmitt trigger connected by an input to the input signal bus is introduced into it, and an output to one of the inputs of the And circuit connected by another input to the output of a Schmitt trigger and the output to one of the inputs of the OR circuit, the other input of which is connected to the input signal bus, and the output to the Schmitt trigger input.

Vn ,.

0g / g J