SU478423A1 - Threshold device - Google Patents

Description

(54) THRESHOLD DEVICE

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The invention relates to automation and computing technology and can be used as an element of analog-digital converters, digital meters, phase meters, devices, restoring pulses.

Known threshold device made according to the Schmidt trigger scheme, coflej driving the input and output transistors with emitter-base coupling to menade transistors, a resistor connected to the collector-base feedback circuit, the input transistor and the voltage divider of the resistors connected to the input base transistor.

However, the known device has an insufficient speed and low stability of the threshold levels of the operation and release voltage.

The aim of the invention is to increase the speed and stability of threshold levels of actuation and release voltages.

To do this, in series with a resistor in a bell-base reverse circuit

The input transistor connection additionally includes a delay line, with the input of the delay line connected to a resistor, and the output to the connection point of the voltage divider of the resistors with the base of the input transistor.

In the drawing, e is the circuit diagram of the device.

The threshold device contains an input transistor 1 trigger, an output transistor 2, an additional resistor 3 connected between the base of the input transistor and the trigger input, resistors 4.5, providing bias on the base of the input transistor 1, negative feedback resistor 6, collector resistors 7, 8 input and output transistors, a resistor 9 of a collector-base feedback, an emitter resistor 1O-, a base resistor 11 of transistor 2, an accelerating capacitor 12, a delay line 13.

The device works as follows: manner.

In the initial state, transistor 1 is closed, and transistor 2 is open. The input voltage Up of the trigger decreases. As the input voltage decreases, the input transistor 1 gradually opens and the potential of its collector increases. At the same time, the potential of the output transistor base also increases. When the input voltage reaches the threshold level Up Up, the output transistor 2, the output of saturation, begins to close. An avalanche-like tipping process occurs in the device, during which the potential of the emitters of transistors 1.2 increases, the potential of the vector and the base of the output transistor 2 increases, and it abruptly closes with the closing of the output transistor 2. The steep rise of the collector potential of the input transistor 1 is transferred via resistor 6 to delay line 13. If the duration of the regenerative stage of the trigger is equal to r, then for the delay time of the 13Pi line, the positive collector voltage of the input transistor 1 jumps to its base after the regeneration stage ends in trigger -here At the end of the process, an additional positive mixing is supplied to the base of the input transistor 1 from its collector through the resistor 6. In this state, the trigger remains until the input voltage Up is increased. When this voltage increases, the input transistor 1, being in the active region, starts to close, the potential of its collector and the base potential decrease. As the input voltage Up rises to a different threshold level U Up, the output transistor 2 begins to open and a regenerative reverse tilt process occurs in the trigger. In the regeneration stage, with the closing of the output transistor 2, the potential of the emitters decreases, the input transistor 1 opens abruptly, the potential of its collector decreases through the RC chain / resistor 9, the capacitor 12 / is transmitted to the base of the output transistor 2, further opening it, etc. At the same time, the negative difference in the collector voltage of the input transistor 1 through the resistor 6 and the line 13 from the fall to iTj is transmitted to the base of the input transis of track 1. At the end of the regenerative stage, to the base of the input transistor 1 from its collector. In the absence of a negative feedback circuit from the collector to the base of the input transistor 1, the hysteresis U. reaches units of volts. When the resistor 6 is switched on from the collector of the input transistor 1, additional mixing is applied to its base, causing the neck to increase the threshold level Up and decrease the level. , p, which leads to a decrease in the difference j - it.e. to reduce hysteresis. When a resistor 6 is turned on between the collector and the base of the input transistor 1, the total gain of the positive feedback loop of the Schmidt trigger during the regeneration stage decreases, resulting in an increase in the duration of the regeneration stage, i.e. to the deterioration of the trigger speed and the deterioration of its reliability. To increase speed, a negative delay line 13 is included in the negative feedback circuit, the inclusion of which, with a delay time Td p, dramatically increases the gain of the positive feedback loop during regeneration due to an increase in the total resistance between the collector and the base of the input transistor A current at the output of line 13 appears with some delay relative to the current at its output. The feature of switching on the delay line is that a sharp drop in the collector voltage delayed by time c is released at its output, which makes it possible to further increase the Schmidt trigger speed and clearly fix threshold levels as soon as the collector voltage of the input transistor 1 appears the output of the line is delayed. 13. Subject of the invention. The threshold device, implemented in accordance with the Schmidt trigger scheme, contains input and output transistors with emitter and collector-base connection between frame, a resistor connected in series kollentorno-base feedback transistor and the input voltage divider of resistors connected to the base

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input transistor, distinguish-the input transistor is additionally included. e e so that, in order to increase the delay line, the input line

the speed and stability of the threshold delay connected to a resistor, and the output

voltage levels of operation and release-- to the junction point of the voltage divider

Cani, in series with the resistor B5 of the resistors with the base of the input transiscep of the collector-base feedback.

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