SU1345319A1 - Schmitt flip-flop - Google Patents

Abstract

. The invention relates to a pulse technique. The aim of the invention is to improve the noise immunity of the trigger. To achieve this goal, five resistors 3–7, three photodiodes B, 9 and 10, and two LEDs 11 and 12 are additionally inserted into the trigger. In addition, the trigger contains two MOS transistors 1 and 2, an electrical input 13, and a power supply bus 14 , common pin 15, output 16, inverse optical output 17. The choice of optimal resistor values is made according to the calculated formulas given in the description of the invention. At the output of the trigger, stable signals are formed that do not depend on the noise on the input, in particular, on the deviation of the input signal level from the required value. 1 il. with (L with 4 JV CO with

Description

one

The invention relates to a pulse technique.

The purpose of the invention is to increase the noise immunity of the trigger.

The drawing shows the Schmitt trigger.

The device contains the first 1 and second 2 MOS transistors with a p-type channel, the first 3, the second 4, the third 5 fourth b and fifth 7 resistors, the first 8, the second 9 and the third 10 photodiodes, the first 11 and the second 12 LEDs In this case, the electrical input 13 of the trigger is connected via the fifth resistor 3 to the cathode of the second photodiode 9, the anode of which is connected to the first. the output of the second resistor 4 n to the gate of the first MOS transistor 1, which through the first photodiode 8 is connected to the source of the first MOS transistor 1, the drain of which is connected to the anode of the first LED 1 1, the first terminal of that resistor 7 is connected to the anode of the third photodiode 10 and with the gate of the second MOS transistor 2, the drain of which is connected to the first output of the third resistor 5 and to the cathode of the second light-emitting diode 12, the anode of which through the fourth resistor 6 is connected to the Shuy power source 14 which also connects the cathodes of the first 8 and third its 10 photodiodes and the source of the second MOS transistor 2, the second terminals of the second 4, third 5 and fifth 7 resistors and the cathode of the first light-emitting diode 11 are connected to a common 15, in addition, the first LED 1 1 opt1; with the 8G and the third 10 photodiodes and with the direct optical output 16 of the circuit, and the second LED 12 is optically coupled to the second photodiode 9 and with the inverted optical output 17 of the circuit.

The selection of the value of the resistors can be made using the following calculated ratios:

and in - and FD 2 - and SI) 1 - and 3 n

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thirty

35

-threshold voltage of ignition of the first LED;

P5, is the threshold ignition voltage of the second LED;

- Threshold current ignition of the first LED;

- Threshold current ignition of the second LED;

- working current of the first LED;

- working current of the second LED;

voltage drop across the illuminated second photodiode;

voltage drop across the illuminated third photodiode;

K is the transfer coefficient of the optron;

t1, voltage input voltage;

power supply voltage;

and l is the insensitivity voltage of the gate-source of the closed MOS transistor. The trigger works as follows.

in the initial state on the direct output 16 of the trigger - O, i.e. first led. 11 does not emit light, but at the inverse output 17 - 1, therefore, the second light-emitting diode 12 is lit, the first 1 and second 2 MOP-toanzistors are locked and the current from the power supply 14 flows through the fourth resistor 6, the second light-emitting diode 12, waking it off Glow, m third resistor 5 to ground. The optical signal from the inverse output 17 is supplied to the second photodiode 9, lowering: its threshold is unlocked.

Pa input trigger 13 receives an electrical signal corresponding to p

0

1, and through the first resistor 3, the second photodiode 9 n, the second resistor 4 begins to flow an electric current, creating a voltage drop across resistors 3 and 4. When the voltage drop across the second resistor 4 applied to the gate of the first MOS transistor 15 becomes higher than the threshold ignition voltage of the first LED II, a positive voltage drop will occur on the gate drain electrodes of the first MOS transistor, which will unlock the first MOS - transistor 1 and current flowing through the light-emitting diode 11, as a result of which the latter will begin to emit light and at the direct output 16 of the circuit an optical signal appears, which corresponds to the presence of a signal 1 on it. The optical link of the first LED 11 to the first 8 and third 10 photodiodes of the latter decouples, through the fifth resistor 7 the current from the power source 14 starts to flow, falling on the fifth resistor 7 the voltage drop applied to the second MOS transistor 2. When the voltage drop across the first resistor 7 exceeds the voltage drop across the third resistor 5, a positive voltage drop occurs on the gate-drain electrodes of the second MOS transistor 2, which causes it to unlock and current flowing through it ka 14 power. As a result, the current flowing through the fourth resistor 6, the second light-emitting diode 12 and the third resistor 5 will decrease to such a value that the second light-emitting diode 12 will go out and there will be no optical signal at the inverse optical output 17 of the circuit, which is equivalent to O. In addition, the optical signal to the second photodiode 9 will not be received and the latter is forbidden to pass the electrical signal from the input 13 of the circuit. The voltage drop across the gate of the first MOS transistor 1 will be kept constant due to the flow of current from the power source through the open first photodiode 8 and the second resistor 4. Due to this, the trigger output signals will be stable and will not be affected by interference at the input, in particular deviation of the input signal from the desired value.

So, at the direct output 16 - 1, at the inverse output 17 - O.

When the input signal O at the input 13 of the circuit, which corresponds to the potential of the common bus 15, part of the current flowing through the second resistor 4, branches the second photodiode 9 to the first resistor 3, which leads to a decrease in the voltage drop on the second resistor 4 applied to the gate of the first MOS transistor t, and ultimately to the locking pos45319

At the outgoing 16, there is no optical signal, which corresponds to O, and the optical connection of the first LED 11 to the first 8 and third 10 photodiodes is interrupted, and the latter are locked, and the voltage decreases. the voltage across the fifth resistor 7 applied to the gate of the second MOS transistor 2. The latter is closed, resulting in an increase in the amount of current flowing through the fourth resistor 6, the second LED 12 and the third resistor 5 to the threshold value azhigani second LED 12, and the latter is ignited, which means the presence of

20 at the inverse output 17 of circuit I. In addition, this optical signal is supplied to the second photodiode 9, and the circuit is again ready for operation.

Claims (1)

25 claims The Schmitt trigger contains first and second MOS transistors, the sources of which are connected to the power supply bus, characterized in 30 that, in order to increase the noise immunity of the trigger, the first, second, third, fourth and fifth resistors, the first, second and third photodiodes, the first and second light 35 emitting diodes are inserted into it, the first output of the first resistor is connected to the electrical input of the circuit, the second the output of the first resistor is connected to the cathode of the second photodiode, the anode of which is connected to the first output of the second resistor and to the gate of the first MOS transistor, which through the first photodiode is connected to the source of the first MOS transistor The first terminal of the fifth resistor is connected to the anode of the third photodiode and to the gate of the second MOS transistor, whose drain is connected to the first terminal of the third resistor and to the cathode of the second light emitting diode whose anode is connected to the power supply bus through the fourth resistor which also connects the cathodes of the first and third photodiodes and the drain the second MOS transistor, the second pins of the second, third, and fifth resistors and the cathode of the first light-emitting diode are connected to the bus bar, 51345319. 6 In addition, the first LED of the optical circuit, and the second LED, is optically coupled to the first and third photodiodes, to the second photodiode and to the india, and to the direct optical output and to the full optical output of the circuit.