Circuit configuration for setting the operating point of a radiofrequency transistor and amplifier circuit

An amplifier circuit with a radiofrequency transistor has a circuit for setting the operating point. The setting circuit provides a base current for the radiofrequency transistor depending on the voltage drop across a resistor that is connected into the collector circuit of the radiofrequency transistor. The circuit has a differential element, which is fed by the supply voltage and compares the voltage drop across the resistor with a reference voltage. The base current is generated by a current source in dependence on the voltage difference. The circuit requires only a low supply voltage, with the result that the power consumed in the resistor is also low. The circuit can be implemented with a small number of components.