SU1246341A1 - Element with controlled resistance - Google Patents

Abstract

The invention relates to analog computing and can be used in voltage controlled attenuators and balancing measuring bridges. The purpose of the invention is to expand the dynamic range. The device contains two field-effect transistors (PT) 1 and 2, four resistors (P) 3,4,5 and 6, an analog voltage adder (lei) 7 and a control signal source 8. With equal values of resistances RZiAiRZib, as well as when a given voltage is reached at the output of the ASN 7, the voltages at the PT 1 and 2 working on the steep section of the drain x-k are equal. The goal is achieved by the introduction of P 5 and 6 and the ACH 7. 1 il. with S (L N9 4; od CO 4:

Description

The invention relates to analog computing and can be widely used in voltage controlled attenuators, balancing measuring bridges and. other radio technology devices.

The purpose of the invention is to expand the dynamic range.

The drawing shows an electrical schematic diagram of an element with controlled resistance.

The proposed element contains the first 1 and second 2 field effect transistors, the first 3, the second 4, the third 5, and the fourth 6 resistors, the analog voltage adder 7, and the control signal source 6.

The element with controlled resistance works as follows.

For the drain current of the field effect transistor on a steep section of stock characteristics

and

s

Id 1 2 (U3, -U,) and, -and ,, W .., (1) where k

to .- specific steepness

MIS transistor J and, - threshold voltage and ,, - gate voltage-source and drain-source, respectively

If you choose the resistance values of the first 3 and second 4 resistors and the third 5 and fourth 6 resistors are equal, ie; Rj R, R Rfc, the voltage on the gate of the first field-effect transistor 1 is

and

N

Uds,) / 2 ..

(2)

Substituting the value of equality (2) into expression (1), is obtained for the drain current of the first field-effect transistor 1

(IN - UT.) And

ds,

(3)

where U- - source voltage 8

control signal, i.e. the drain current of the first field-effect transistor 1 linearly depends on the drain-source voltage on the steep portion of the characteristic.

VNIISH Order 4020/54

Circulation 8X6

Subscription .- Yoligr GPR - Chiyo, Uzhgorod, st. Project, 4

At the output of the analog adder 7 voltages, you must provide a voltage

year

and, - + and

ds,.

(four)

ten

Substituting the value (4) in the high-kink (1) for the drain current of the second field transistor 2, we obtain

k. 2

(U ,, - 2U,) (U ,, - Uj,) ,. (five)

where Ugjjf is the output voltage of the device,

For identical transistors, i.e. k, C, U- - t., is obtained from the ratio:

.( one

47

following ratio 20

Ucnyt 2Ud5,

THAT shows the equality of voltage drops on field-effect transistors 1 and 2, working on a steep part of the drain characteristics.

Claims (1)

Invention Formula An element with controlled resistance, made in the form of serially connected first and second field-effect transistors, the source of the first field-effect transistor is connected to the common bus, the gate of the first field-effect transistor is connected to the drain of the first field-effect transistor and the source of the control signal, respectively, through the first and second resistors, and the drain The second field-effect transistor is an output element with a controlled resistance, characterized in that, in order to expand the dynamic range, between the drain of the first across evogo transistor and the gate of the second field effect transistor are series connected analog voltage adder, the second input of which is connected to a source of a control signal, and a third resistor, and between the gate and the drain of the second field effect transistor including the fourth resistor. Circulation 8X6 . Uzhgorod, st. P