Bipolar transistors with control of electric field

Abstract

The invention provides a bipolar transistor circuit and a method of controlling a bipolar transistor, in which the bipolar transistor has a gate terminal for controlling the electric field in a collector region of the transistor. The bias voltage applied to the gate terminal is controlled to achieve different transistor characteristics.

1 . A transistor circuit, comprising:
 a bipolar transistor comprising a base, collector and emitter, and at least one gate terminal for controlling the electric field in a collector region of the transistor;   a control circuit for controlling a bias voltage or bias voltages applied to the gate terminal or gate terminals, with different control voltages used for different transistor characteristics.   
     
     
         2 . A circuit comprising:
 at least first and second first transistor circuits as claimed in  claim 1 , wherein the transistors of the first and second first transistor circuits are identical and have different bias voltages applied to them to achieve different transistor characteristics.   
     
     
         3 . A circuit as claimed in  claim 1 , further comprising:
 a feedback circuit for dynamically controlling a bias voltage applied to the gate terminal in dependence on a collector emitter or base-emitter voltage of the bipolar transistor.   
     
     
         4 . A circuit as claimed in  claim 3 , wherein the feedback circuit comprises an inverter connected between the collector and gate terminal. 
     
     
         5 . A circuit as claimed in  claim 2 , wherein the dynamic control is at the frequency of operation of the bipolar transistor. 
     
     
         6 . An RF power amplifier comprising a circuit as claimed in  claim 1 . 
     
     
         7 . A method of controlling a bipolar transistor comprising a base, collector and emitter, and at least one gate terminal for controlling the electric field in a collector region of the transistor, wherein the method comprises:
 controlling a bias voltage or bias voltages applied to the gate terminal or terminals to achieve different transistor characteristics.   
     
     
         8 . A method as claimed in  claim 7 , comprising controlling first and second first transistor circuits, wherein the transistors of the first and second first transistor circuits are identical, and the method comprises applying different bias voltages to the transistor of the first and second first transistor circuits to achieve different transistor characteristics. 
     
     
         9 . A method as claimed in  claim 7 , further comprising dynamically controlling a bias voltage applied to the gate terminal in dependence on a collector emitter voltage of the bipolar transistor. 
     
     
         10 . A method as claimed in  claim 9 , comprising generating a bias voltage from an inverted version of the collector voltage. 
     
     
         11 . A method as claimed in  claim 9 , wherein the dynamic control is at the frequency of operation of the bipolar transistor.