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LOW IMPEDANCE, TEMPERATURE COMPENSATED BIAS SUPPLY

IP.com Disclosure Number: IPCOM000005480D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2001-Oct-08
Document File: 1 page(s) / 61K

Publishing Venue

Motorola

Related People

Bob Gunther: AUTHOR

Abstract

Low impedance and temperature compensation are desirable characteristics of a bias source to be used with a transistor SSB linear amplifier. Low impedance to prevent shift in operating point with changes in drive and temperature compensation to hold the operating point over the temperature range. The following circuit satisfies both requirements with the ability to adjust the slope (MVI'C) to match the linear amplifier operating condition.

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@ MOTOROLA Technical Developments Volume 3 March 1983

LOW IMPEDANCE, TEMPERATURE COMPENSATED BIAS SUPPLY

By Bob Gunther

   Low impedance and temperature compensation are desirable characteristics of a bias source to be used with a transistor SSB linear amplifier. Low impedance to prevent shift in operating point with changes in drive and temperature compensation to hold the operating point over the temperature range. The following circuit satisfies both requirements with the ability to adjust the slope (MVI'C) to match the linear amplifier operating condition.

'".. Two temperature sensing, diode connected, transistors Qt, Q2 are used to establish a voltage pro- portional to the temperature of the transistor being biased by the invention. This temperature depen- dent voltage is applied to the minus input of an op amp (operational amplifier) U through a voltage divider R2. The output of U1 is directly connected to the base of an NPN transistor b 3. The collector of Q3 is the bias point for the stage to be biased. The positive input of Ut is also connected to the collec- tor of Q3 through a resistive divider R4 and R5, closing the feedback loop. The high open loop gain of the op amp and transistor provides a highly stabilized bias voltage for the linear amplifier stage.

   The temperature sensors Qf - Q2 must be thermally coupled to the transistor of the stage to be biased. Rf supplies a near constant current for Ql, Q
voltage across Qt, Q

.'

and R2. R2 determines the pro...