SU644034A1 - Comparator - Google Patents

Description

(54) COMPARATOR

pa is connected via diodes to the base and, and drain and source respectively to the emitters of the transistors of the differential cascade.

The drawing shows a schematic diagram of a comparator.

The comparator contains a differential cascade on bipolar transistors 1 and 2, sources of currents 3 and 4 in their emitter circuits, a unipolar transistor 5 connected by a drain and a source, respectively, to the emitters, and a gate through diodes 6 and 7 to the bases of the bipolar transistors connected to the inputs 8 and 9 of the device. A load 10 is connected between the collectors of the bipolar transistors 1 and 2.

The device works as follows.

The voltage across the gate of the transistor 5 is always equal to the smaller of the two input voltages selected by diodes 6 and 7. If the input voltages are equal, then the emitter potentials of the bipolar transistors 1 and 2. Transistor 5 is a linear resistance and sufficiently low currents of current generators 3 and 4 this resistance can be neglected. In this case, the circuit is equivalent to the usual differential cascade. With a decrease in the voltage Ui at the input 8, the transistor 1 of the differential stage is closed and the currents of the current generators 3 and 4 flow through the transistor 2 of the differential stage. Transistor 5 operates in a controlled linear impedance mode until the input differential voltage reaches a predetermined cutoff voltage equal to the gate-source voltage, at which the current in the pass-through characteristic of the transistor 5 is equal to the current of the current generator 3. Then, the reverse voltage of the emitter junction of transistor 1 stops increasing as the transistor 5 goes into the source follower mode, while

I

potential of the emitter of transistor 1 "is following

beyond the base potential. When changing the sign

the difference between the input voltages is closed by the transistor 2 and the currents of the tsk generator 3 and 4 will flow through the transistor 1. Due to the symmetry of the characteristics of the unipolar transistor 5, all the electrical processes described above are repeated for the right shoulder of the differential cascade.

Thus, the allowable differential signal of the proposed comparator is limited only by the permissible interelectrode voltages of the unipolar transistor, which, as is well known, for certain types of unipolar transistors (for example, for transistors with a MIS structure, can be quite large, which causes a small comparison error.

The use of a single field-effect transistor simplifies the proposed device. High performance parameters — a large range of compared voltages, high input resistance, increased comparison accuracy — extend the functionality of the comparator and allow it to be used as a basic element of time-pulse systems.

Claims (2)

1.Shilo VL. Linear integrated circuits in radio electronic equipment. M., “Owls. Radio, 1974, p. 181 - 196. 2. US patent number 3489919, cl. 307-202, 1970. R