SU951684A1 - Comparator - Google Patents

Description

(Sk) COMPARATOR

The invention relates to radio engineering and electronics and can be used in automation and computing devices. Comparators are known that contain an input transistor differential cascade with an active load, the power input of which is connected to the output of a current generator, and an output cascade, made according to a circuit with a common emitter, on the transistor of the same type of conductivity as that of the active load transistor, the input of which is connected to the output of the differential stage 1. The disadvantage of the known comparator is e a small performance. The purpose of the invention is to increase the speed of the comparator. The goal is achieved by the fact that the comparator containing the input transistor differential cascade with an active load, the power input of which is connected to the output of the current generator and the output stage j performed according to the common emitter circuit, on the transistor of the same type of conductivity as the active load transistor, which is connected to the output of the differential cascade, a voltage source and an additional transistor, having a conductivity type identical to an active load transistor, the emitter co orogo connected to the output of the differential stage, the collector - to output of said current generator and the base - with the source output reference voltage. The drawing shows a schematic diagram of a comparator. The comparator contains an input differential stage 1 with a resistive load 2, the power input of which is connected to the output of the current generator 3, and the output to the input of the output stage k on a transistor connected

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under the scheme with a common emitter. The emitter of the additional transistor 5 is connected to the output of the differential stage 1, the collector is connected to the output of the current generator 3, the base is connected to the output of the reference voltage source 6. The reference voltage source 6 contains, for example, serially connected collector-emitter sections of the saturated transistor 7 and directly The base-emitter junction of the transistor in the diode switching on 8, Inputs 9. and 10 of the differential stage 1 are the inputs of the device, and the output 11 of the stage is its output.

The comparator works as follows.

If in the initial state the potential; the first input 9 of the comparator is lower than the potential of the second input 10, the T9 output of the differential stage 1 is low potential, and the output stage transistor is locked The comparator output 11 has a potential close to the supply voltage. The potential on the basis of the additional transistor 5 given by the source of the reference voltage 6 is equal to the sum of the voltage on its base-emitter junction and the fully open resistor of the active load 2. In this case, the additional transistor 5 is open and part of the current of the current generator 3 flows through n & into active load 2, preventing the transistor entering into it from becoming deeply saturated.

The spasmodic lowering of the potential of input 10 relative to input 9 causes a rapid increase in voltage at the output / differential circuit 1, opening the output stage transistor and reducing the potential of output 11 to a level close to zero. The additional transistor 5 is closed, since the potential from the source of the reference voltage 6 is applied to its base below the sum of the base-emitter voltages of the transistor 5 and the voltage 4

nor unlock the output transistor t.

In the prototype, switching occurs with a significant delay, so

As in the initial state of the transistor, the resistive load is in deep saturation and additional time is required to dissipate the excess charge in its base circuit.

Improving the speed achieved with a low voltage supply of 3-5 V and a slight increase in current consumption. The amount of additional current required for operation

the reference voltage source is only 0.1 of the magnitude of the current consumed by the differential stage. comparator house

Formula and: acquisitions

A comparator containing an input transistor differential stage with a resistive load, the power input of which is connected to the output of the current generator, and an output stage executed according to a common emitter circuit on a transistor of the same type

conduction, as in the active load transistor, the input of which is connected to the output of the differential cascade, characterized in that, in order to improve speed, a reference voltage source and an additional transistor are provided; i) the type of conductivity, which is similar to active load transistors whose emitter is connected to the output of the differential stage, the collector to the output of the current generator, and the base to the output of the reference voltage source. Sources of information taken into account in the examination

1. Directory Linear Integrated circuit. Datu book vol. 19, 1978, p. 300 (prototype),

Claims (1)

Claim A comparator containing an input transistor differential cascade with a resistive load, the power input of which is connected to the output of the current generator, and an output cascade, made according to a common emitter circuit, on a transistor of the same type of conductivity as the active load transistor whose input is connected to the output differential cascade, characterized in that, in order to improve performance, a voltage reference source and an additional transistor having a conductivity type identical to the transistors of an active load are introduced ki, whose emitter is coupled to an output of the differential stage, the collector - with an output of said current generator and the base - with the output of the reference voltage source.