Browse Prior Art Database

BIASING SCHEME FOR ENHANCED POWER AMPLIFIER STABILITY AND GAIN IMPROVEMENT

IP.com Disclosure Number: IPCOM000009452D
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2002-Aug-26
Document File: 2 page(s) / 79K

Publishing Venue

Motorola

Related People

Chow Yut Hoong: AUTHOR

Abstract

Proposed below is a biasing scheme to reduce The schematic below details a general rf power the susceptibility of an rf MOSFET power amplifier amplifier using an rf power MOSFET. to instability tendencies.

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Page 1 of 2

Developments Technical 0 M MOTOROLA

BIASING SCHEME FOR ENHANCED POWER AMPLIFIER STABILITY AND GAIN IMPROVEMENT

by Chow Yut Hoong

Proposed below is a biasing scheme to reduce The schematic below details a general rf power

the susceptibility of an rf MOSFET power amplifier amplifier using an rf power MOSFET. to instability tendencies.

Id

To rest of output match circuit

  In existing circuit designs, Xl is either a high value resistor to decouple the input matching circuit from the gate bias circuitry, or a low value resistor to improve the stability of the amplifier. In the former case, Xl is typically 10 KS2 while in the latter, Xl ranges from 509 to 1009. Stability is also enhanced by the addition of feedback resistor Rl . This resistor will enhance low frequency operation and reduce susceptibility to low frequency type of oscillations.

The lower the value of Rl, the more stable the amplifier will be. However, reducing Rl too much will cause the amplifier drain current (Id) to increase for the same output power and the amplifier will then be inefficient. Thus, the value of Rl chosen is a tradeoff between stability and efficiency. Typical values of Rl are a few hundred Ohms. Cl is a cou- pling capacitor of negligible impedance.

0 Motomla. 1°C. ,999 96 September 1999

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Developments Technical 0 M MO-LA

  The biasing scheme proposes replacing Xl with a low value inductance. Ll is typically a few nH's to...