RU1803966C - Threshold device - Google Patents

Abstract

Application: pulse electronics, receiving devices, automation and control for generating pulse signals from a mixture of signal and noise. SUBSTANCE: threshold device contains a static synchronous D-trigger. In order to simplify while maintaining noise immunity, three resistors are introduced, one of which is connected between the direct output and the trigger C input, the other between the trigger C and D inputs, and the third between the trigger D input and the device input. To increase the noise immunity, a diode is introduced into the device, the anode of which is connected to the direct output, and the cathode is connected to the trigger C-input. 1 s.p. f-ly, 2 ill.

Description

The invention relates to pulsed electronics and can be used in reception, automation and control devices to generate pulsed signals from a mixture of signal and noise.

The purpose of the invention is to simplify the device while maintaining noise immunity.

For this, a threshold device containing a static synchronous D-trigger (e, three resistors and a diode are introduced, the anode of which is connected to the direct output of the trigger, and the cathode is connected to the C-input, the D-input of the trigger is connected through the first resistor with the input of the device, through the second resistor - with the C-input, which is connected through the third resistor to the direct output of the trigger.

SUMMARY OF THE INVENTION 1 and timing diagrams in FIG. 2, where a is the input voltage EBx; b - voltage at the C-input, Ec; c - voltage at the D-input, Ed; g is the output voltage.

The threshold device contains D-trigger 1, diode 2, resistors 3-5, the anode of diode 2 is connected to the direct output of trigger 1, and the cathode with C-input, D-input by resistor 3 is connected to the input of the device, and resistor 4 is with a C input, which is connected by a resistor 5 to the direct output of the trigger.

As elements of the device, for example, the following commercially available products can be used: D-flip-flop - chip 133TM5, diode-diode assembly 2DS607A, resistors - block B19.

The threshold device operates as follows.

At the initial moment, when the input signal is zero at the C- and D-inputs and the trigger output, the logic level is set to zero (about zero volts (3)).

With an increase in the input signal (Fig. 2a, the trapezoidal signal is conventionally shown), the voltages at the D and C inputs increase.

ate

with

00

about

with u a

ON

Resistors 3-5 are selected so that the voltage at the D input increases faster than at the C input. At point 1, the voltage at the D input reaches the trigger switching threshold at the D input, but at the C input, the voltage is below the threshold and switching does not occur. At point 2, the voltage at the C-input reaches the switching threshold, and since the voltage at the D-input is higher than the threshold, switching occurs, and increases the voltage at the C- and D-inputs more strongly than the trigger output through diode 2. In Fig. 2, a voltage of 1.5 V is adopted as a threshold at the input of the microcircuits, and a high level voltage at the output of 3 V ((3), p. 60). With a further increase in the input voltage, the diode 2 closes, the voltages at the D-m C inputs increase (to point 3), but the state of the trigger does not change.

As the input voltage decreases (between points 4 and 5, Fig. 2a), the pattern repeats (as between points 2 and 3). At point 5, diode 2 opens and the voltage of the C-input remains almost unchanged (due to the diode), and the voltage of the D-input drops. At point 6, the voltage of the D-input reaches the threshold, and since at this moment the voltage at the C-input is higher than the threshold, the trigger switches. The voltages of the C and D inputs drop to almost zero.

When the power source is turned on, the initial setting of the trigger is always in the zero state, since with a zero input signal and a random single output, a switching effect acts on the D-trigger, forcing it to force it to the required initial position.

The selection of the resistor ratio is determined by the required switching thresholds of the device. Thresholds without taking into account the influence of the diode and the variation in the output voltage of the trigger can be determined:

on C-input (tripping voltage):

(1 +

R3 + R4 R5

-) Ep;

5

0

5

0

5

by D-input (release voltage) in the absence of a diode:

O-nyJ O. 1Ek) EP;

R4 + R5

R3

in the presence of a diode: (1-) Ep.

Since the switching of the device occurs at the maximum (threshold C) and minimum (threshold D) values of the output levels of the microcircuits, the noise immunity of such a device is approximately twice as high as that of simple triggers.

Claims (2)

1. A threshold device containing a static synchronous D-flip-flop, characterized in that, in order to simplify while maintaining noise immunity, three resistors are introduced into it, the first is connected between the direct output and the C-input of the trigger, the second is between C and D-inputs trigger, the third - between the D-input of the trigger and the input of the device. 2. The device according to claim 1, characterized in that, in order to increase the noise immunity, a diode is introduced, the anode of which is connected to the direct output, and the cathode is connected to the trigger C-input.