A-ab transconductor

Abstract

The invention relates to a transconductor, comprising means for automatic selection of a nonlinear function of class A or a linear function of class AB from an input signal for processing and for automatic adjustment of the current drawn from a supply to a level necessary for the functioning thereof.

1 . A transconductor, including means for automatically selecting a non-linear class A operation or a linear class AB operation based on an input signal to be processed, and for automatically adjusting the current from a power supply to a level necessary to its operation.  
   
   
       2 . The transconductor of  claim 1 , including at least two bipolar transistors, common bases of which define a first input/output terminal of the transconductor; 
 interconnected collectors of which define a second input/output terminal of the transconductor;    emitters of which are individually connected to a low voltage reference line by a respective impedance; and    the bases of which are connected to a same D.C. current source.    
   
   
       3 . The transconductor of  claim 2 , wherein the impedances of each individual connection of the emitters of the two bipolar transistors to the low voltage reference line are only resistive.  
   
   
       4 . The transconductor of  claim 2 , wherein the bases are connected to the D.C. current source by an isolating resistor.  
   
   
       5 . The transconductor of  claim 3 , wherein the ratios of the isolating resistance to the resistance of the individual connection of the emitters to the reference line are different.  
   
   
       6 . The transconductor of  claim 4 , wherein the two bipolar transistors are of different sizes, and wherein the impedance of the individual resistive connection of each of their emitters to the voltage reference line is implemented by a respective resistor.  
   
   
       7 . The transconductor of  claim 2 , wherein the D.C. current source is formed by the connection, between a high supply line and the low voltage reference line, of a D.C. current source and of a first bipolar transistor of a given type, the junction of the current source and of the first transistor being connected to the base of a second bipolar transistor of the same type as the first transistor, a collector/emitter terminal of which is connected to the high supply line and an emitter/collector terminal of which is connected to the base of the first transistor and forms the current source output.  
   
   
       8 . The transconductor of  claim 7 , wherein a resistor is interposed between the base of the first bipolar transistor and the emitter/collector terminal of the second bipolar transistor forming the output of the D.C. current source.  
   
   
       9 . Input/output stage of a mixer or of a power amplifier or of a low-noise amplifier, formed of a transconductor according to  claim 1.