SU1357860A1 - Two-threshold comparator - Google Patents

Abstract

The invention relates to a measurement technique and can be used to determine the voltage output from a set range, as well as a differential discriminator. The aim of the invention is to expand the range of level control and improve accuracy. To achieve the goal, a device containing a dual comparator 1, resistors 2 and 3, power sources 6 and 7, a field-effect transistor 13 and a resistor 14, additionally introduced a pnp-transistor 4, pnp-transistor 5 , two voltage dividers 8 and 9, resistors 10 and 11, variable resistor 12. By varying the resistance of resistor 12, setting threshold levels in the positive and negative regions of the range of threshold levels is achieved. 1 hp f-ly, 1 ill. (L 00 ate vj SH) f

Description

one

The invention relates to a measurement technique and can be used to determine the voltage output from a set tolerance, as well as a differential discriminator.

The aim of the invention is to expand the range of level control and improve accuracy.

The drawing shows a two-threshold comparator circuit.

. The two-threshold comparator contains a dual comparator 1, the first 2 and second 3 resistors, a pnp transistor 4, a pnp transistor 5, the first 6 and second 7 power sources, the first 8 and second 9 voltage dividers, trans - Bbrf i 10 and the second 11 additional resistors, a variable resistor 12, a gated transistor 13 and a third additional resistor 14. The first 2 and -second 3 resistors are connected in series. Their common conclusion is connected to

13578602

resistor 10, as well as transistor 5, power supply 7, divider 9, additional 11 and alternating 12, reconstruct two current generators

ten

15

20

respectively on transistors 4 and 5.

Two-threshold comparator works as follows.

The voltage drop on the first resistor 2 determines the lower threshold level, and the upper threshold level exceeds the lower one on the discrimination window, the value of which is equal to the voltage drop on the second resistor 3 from the current of the current generator through transistor 4 flowing through it.

Disregarding, initially, for simplicity, the field effect transistor 13, we find that, when the current flows through the collectors of transistors 4 and 5, the lower threshold level is zero. An increase in the resistance of the variable resistor 12 in the emitter of the pnp transistor decreases the generator current.

the first inverting input is dual 25 current on the transistor 5 and through the first

the first comparator 1. The output of the first resistor 2 is connected to the common bus NOI1. The second terminal of the second resistor 3 is connected to the first non-inverting input of the dual comparator 1, with the gate of the field-effect transistor 13 and the collector of the pn-transistor 4. The base of the transistor 4 is connected to the middle section of the first voltage divider 8, the extreme terminals of which are connected to the corresponding terminals of the first power source 6. The emitter of transistor 4 is connected via the first additional resistor 10 to the positive pole of the first power supply 6. The base of the pnp transistor 5 is connected to the middle terminal of the second voltage divider 9, the extreme terminals of which are connected to the corresponding terminals of the second power source 7. The emitter of transistor 5 is through the second additional resistor 11 and the variable resistor 12 is connected to the negative pole of the power supply 7. The negative pole of the power source 6 and the positive pole of the power source 7 are connected to a common bus. The source of the field effect transistor 13 through the third additional resistor 14 is connected to the common terminal of the first 2 and second 3 resistors. The drain of the field-effect transistor 13 is connected to the emitter of the transistor 4. Transistor 4, power supply 6, divider 8, additional

resistor 10, as well as transistor 5, power supply 7, divider 9, additional 11 and alternating 12, reconstruct two current generators

five

0

respectively on transistors 4 and 5.

Two-threshold comparator works as follows.

The voltage drop on the first resistor 2 determines the lower threshold level, and the upper threshold level exceeds the lower one on the discrimination window, the value of which is equal to the voltage drop on the second resistor 3 from the current of the current generator through transistor 4 flowing through it.

Disregarding, initially, for simplicity, the field effect transistor 13, we find that, when the current flows through the collectors of transistors 4 and 5, the lower threshold level is zero. An increase in the resistance of the variable resistor 12 in the emitter of the pnp transistor decreases the generator current.

resistor 2 flows part of the current generator current on transistor 4 and the lower threshold level becomes positive. The smaller the current generator current on the transistor 5 relative to the constant current generator current on transistor 4, the greater the shift of the lower threshold level into the positive voltage range. The upper threshold of the eight level differs from that of the lower by a voltage drop across the second resistor 3.

Conversely, if the current generator current on the transistor 5 is greater than the current generator current on transistor 4, an excess part of the current generator current on transistor 5 flows through the first resistor 2, which creates a negative voltage on the first resistor 2. The greater the current generator current on the transistor 5 (the lower the resistance of the variable resistor 12 in the pnp transistor 5 emitter), the greater: the shift of the threshold levels in the region of negative voltages. The maximum shift to the negative region of the threshold level range is determined: in the same way as a negative potential based on a np-p-transistor 5.

Thus, by varying the resistance of one variable resistor 12, threshold levels are set to positive and

negative regions of the range of threshold levels.

An additional stabilization of the discrimination window width (increased accuracy) is provided by the field-effect transistor 13. The current through the field-effect transistor 13 is a small, for example, one-tenth, part of the current generator current on the transistor 4. Since the gate current of the field-effect transistor 13 is practically zero, the width the discrimination window is still determined by the voltage drop across the second resistor 3 from the current flowing through it of the current generator on the transistor 4. The lower threshold level when the field-effect transistor 13 is taken into account is zero not equal to the current of the two current generators, and when the generator current on the transistor 5 exceeds the generator current on transistor 4 by the value of the source current of the field-effect transistor 13.

The additional stabilization of the width of the discrimination window is as follows.

When adjusting the threshold levels, the potential of a pnp transistor 4 changes. The effect of varying the base width slightly changes the collector current, for example, when the threshold levels shift to the negative region, the collector current of the pnpn transistor increases, which increases

the voltage drop across the second resistor is connected to the average pe 3. This increases the drain current of the FET 13, the potential of the emitter of the pnp transistor 4 decreases, and the collector current of the pnp transistor 4 restores the original value. When the threshold levels are shifted to the positive region, the drain current of the field-effect transistor 13 decreases if the width of the window is reduced by discriminating the respective resistor voltage dividers, the extreme ends of which are connected to the corresponding terminals of the respective power sources, the emitter of the pnp-rn transistor is connected through the positive pole of the first power source, the emitter of the pnp transistor through a series connected second additional resistor and a cross-connect resistor n to the negative pole of the second power source, the collector p-n-p transistor is connected to a second vtod second resistor, and whose collector is n-p-n transistor is connected to the common terminal of the first and second resistors.

As a result, the current of the pnpp transistor 4 collector increases and the window width is stabilized. When using a field-effect transistor 13 with an initial drain current constituting a small part of the rated current of the current generator on transistor 4, the source resistor may be missing.

When the input signal from: source 15 at the output of dual comparator 1 is set to level 1, if the signal lies inside the window, and the level O, if the signal is lower

lower and levels.

higher upper threshold

Claims (2)

1. A two-threshold comparator containing a dual comparator, the first and second power sources, the positive pole of the first of which and the negative pole of the second are connected to the corresponding inputs of the dual comparator, and the negative pole of the first and the positive pole of the second source are connected to a common bus and connected in series the first and second resistors, the first output of the first of which is connected to the common bus, the common output of the first and second resistors are connected to the first inverting input of the dual comparat Pa, and the second output of the second resistor is connected to the first inverting input of the dual comparator, the second inverting and non-inverting inputs of the double comparator are connected to the input terminal, characterized in that, in order to extend the threshold level control range, two transistors are inserted, respectively, with pnp - and p-p-conductivities, the first and second resistor voltage dividers, the first and second additional resistors and a variable resistor, with the base transistors are connected to medium the terminals of the respective resistor voltage dividers, the extreme voltage of which are connected to the corresponding terminals of the respective power sources, the emitter of the pnp transistor is connected to the positive pole of the first source of power through the first additional resistor, and the emitter of the pnp to pn transistor is connected through series the second additional resistor and the transistor resistor are connected to the negative pole of the second power source, the pnpp transistor collector is connected to the second side of the second resistor, and the call The pnp transistor is connected to the common terminal of the first and second resistors. 2. A comparator according to claim 1, characterized in that, in order to increase accuracy, a field-effect transistor and a third additional resistor are introduced, the drain of the field-effect transistor connected to the emitter of a pnp transistor, its source through the third An additional resistor is connected to the stora, and the gate is connected to the second common terminal of the first and second resistor of the second resistor.