Browse Prior Art Database

SUPPLY INDEPENDENT ACTIVE BIAS CIRCUIT

IP.com Disclosure Number: IPCOM000005539D
Original Publication Date: 1984-Apr-01
Included in the Prior Art Database: 2001-Oct-12
Document File: 1 page(s) / 42K

Publishing Venue

Motorola

Related People

Alton P. Werronen: AUTHOR [+2]

Abstract

In a typical transistor bias circuit, stability is achieved through the use of an emitter resistor and reliance on a stable supply voltage. However, the emitter resistor is undesirable. It helps maintain bias stability but has the undesirable effects of degrading noise figure and stability due to imperfect bypassing of the emitter.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

MOTOROLA Technical Developments Volume4 April 1984

SUPPLY INDEPENDENT ACTIVE BIAS CIRCUIT

by Alton P. Werronen and Michael J. Frey

   In a typical transistor bias circuit, stability is achieved through the use of an emitter resistor and reliance on a stable supply voltage. However, the emitter resistor is undesirable. It helps maintain bias stability but has the undesirable effects of degrading noise figure and stability due to imperfect bypassing of the emitter.

   The circuit in figure 1 does maintain stability without an emitter resistor. The uniqueness of this circuit is that the D.C. bias conditions are independent of supply voltage, and one can independently set the collector voltage and collector current by changing a single component for either parameter.

   The circuit uses a zener diode VRl plus the emitter drop of Qi to set the collector voltage on 02. The field effect current regulator diode CR1 sets a constant current, which must be devided between the collector of Q2 and the emitter of 01. The emitter current of Ql is approximately equal to the base current of Q2. Therefore, the current flowing through Ql is that needed to drive the base of Q2, and the collector current of 02 is approximately equal to the current of the current regulator diode.

v+

P CR1

t,

I

Rl

s

I

I

I, Ql

VRl

I

Q2

I'; T

0 Motorola, Inc. 1984 38

[This page contains 15 pictures or other non-text objects]