Single-stage MOSFET amplifier is described which is identical to standard neutralized amplifier except that neutralization provided by broadband transformer is applied to AGC gate instead of signal gate. Neutralization of drain-to-control gate capacity minimizes the phase change induced by variation in AGC

Coffin, R. C.

Lutes, G. F.

English

NASA Technical Reports Server

NASA TECH BRIEF 
NASA Pasadena Office R fl
December 1972
	 B72-10185 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Low Phase-Shift Amplifier 
.
The problem: 
To decrease the phase shift which occurs in the 
output of an amplifier when the automatic gain con- 
trol (AGC) is changed.
Output 
The solution: 
Use a broadband transformer to neutralize the dis-
tributed capacity between the drain and control gate 
of a dual-gate MOSFET. 
How it's done: 
The single-stage MOSFET amplifier shown in the 
diagram is identical to a standard neutralized amplifier 
except that the neutralization provided by a broad-
band transformer is applied to the AGC gate instead 
of the signal gate; this arrangement cancels effects 
attributable to the capacitance existing between the
control gate and the drain. 
There is an RC network which consists of the drain- 
to-control-gate capacity and the channel resistance. 
The channel resistance varies with a change of voltage 
on the control gate and causes the RC time constant 
to change; as a result, there is a change of phase from 
input to output of the amplifier. Neutralization of the 
drain-to-control-gate capacity minimizes the phase 
change induced by variation in AGC. 
The amount of phase shift vs gain in a three-stage 
amplifier was found to be ±as° for a gain change 
from 10 dB to 50 dB. The amplifier will handle signal 
levels up to about one volts rms. The noise figure is 
about 9 dB at 10 MHz when driven from a 1000-ohm 
source. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP72-10185 
Patent status: 
NASA has decided not to apply for a patent. 
Source: George F. Lutes and 
Richard C. Coffin of 
Caltech/JPL 
under contract to 
NASA Pasadena Office 
(NPO-11663) 
Category 01 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
01
https://ntrs.nasa.gov/search.jsp?R=19720000185 2020-03-17T03:32:44+00:00Z


Low phase-shift amplifier

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server