Patent ID: 6215358
Filing Date: 2001-04-10
Classification: H03F

Abstract:
For use in an RF amplifier containing an output power transistor having a quiescent current set at a selected bias current level, a biasing circuit for maintaining said quiescent current at said selected bias level comprising:a temperature sensor circuit capable of generating a temperature-sensitive control voltage that varies according to changes in temperature of said output power transistor; anda bias voltage generating circuit capable of detecting a variation in said temperature-sensitive control voltage and, in response thereto, adjusting a bias voltage applied to said output power transistor by an amount suitable to offset a change in said selected bias current level caused by a temperature change related to said variation in said temperature-sensitive voltage;amplification means for scaling a voltage change in said temperature-sensitive control voltage to match a required voltage change in said bias voltage; andan adjustable voltage divider circuit for further scaling said voltage change in said temperature-sensitive control voltage to match said required voltage change in said bias voltage.