SU1203687A1 - Controlled attenuator - Google Patents

Abstract

The invention relates to radio engineering and is used to automatically adjust gain and other analog signal transforms. The purpose of the invention is to stabilize the output impedance in the UgblX and wi range; (Uynp Control. The gate of the field-effect transistor (PT) 3 receives a control voltage, which establishes some resistance of the channel PT 3. Thanks to feedback through the amplifier 7, the resistance of the channel PT 4 The potential at the connection point of the PT 3 with the PT 4 is automatically maintained close to zero. Thus, the resistance of the parallel circuit formed by the channels PT 3, PT 4 is kept constant and equal to the resistance of the resistor 6. Since PT1, iPT2 4 are similar and are controlled by the same voltage, the attenuator yshrdnoe resistance equal to the resistance of the resistor 6 and is constant over the entire range varying control voltage kntsego. 1 yl. slab with Q

Description

The invention relates to radio engineering and can be used to automatically adjust the gain and other conversions of the analog signal in devices for various purposes.

The aim of the invention is to stabilize the output resistance in the control range.

The drawing shows a circuit diagram of a controlled attenuator.

The controlled attenuator contains the first 1j second 2, third 3 and fourth 4 field-effect transistors, the midpoint voltage source 5, the resistor 6 and the DC amplifier 7.

Managed attenuator works as follows.

The gate of the third field-effect transistor 3 receives a control voltage, which establishes some resistance of the channel of this transistor. Due to the feedback, the resistance of the channel of the fourth field-effect trans 4, the potential of the third field-effect transistor 3 to the drain of the fourth field-effect transistor 4 at the source connection point of the third field-effect transistor 4 is automatically maintained close to zero regardless of changes in the control voltage and, consequently, the parallel resistance The circuit of the circuit formed by the channels of the field-effect transistors 3 and 4 is kept constant. Thus, equality is maintained.

g- 1

 R.

where g ,,

M g.

resistances of the field-effect transistors 3 and 4,

R is the resistance of the resistor 6.

The output impedance of the divider, made up of field-effect transistors 1 and 2, P1) and provided that the impedance of the input source n) is negligible.

VNIIPI Order 84: 9/60 Circulation: 871 Subscription Branch PGS Patent, Uzhgorod; ul.Proektna, 4

R

 G, g:

8S

+ Y

G - Channel Resistance

where r

field effect transistors

1 and 2.

Since field-effect transistors 1 and 3, as well as field-effect transistors 2 and 4 are of the same type and are controlled by the same voltage, then r g

H

Therefore, the output

controlled attenuator resistance

R

Bbix

 R.

five

five

0

five

0

0

Those. is constant over the entire range of control voltage.

Claims (1)

Invention Formula A control attenuator containing a l-shaped link formed by perm and second field-effect transistors, as well as a third and fourth field-effect transistors, the gate of the second field-effect transistor connected to the gate of the fourth field-effect transistor, and the gates of the first and third field-effect transistors are combined and are the input control, in order to stabilize the output resistance of the attenuator in the control range e, a voltage source with a midpoint is inserted into it This current, the source of the third field-effect transistor is connected to the drain of the fourth field-effect transistor and connected through a resistor to one voltage source bus with a midpoint, and through an amplifier POSITION {o-oo I OKa with the gates of the second and fourth field-effect transistors, the drain The third field-effect transistor and the source of the fourth field-effect transistor are connected to a second voltage source bus with a midpoint, while the structure of the first and third field-effect transistors is the same and the counter-shield is the second and fourth th field effect transistors.