Abstract:
A biasing device includes closed-loop transconductance slaving circuit, able to slave the time average of the base/emitter or gate/source voltage of the amplifier transistor (Q1) to a reference voltage corresponding to a desired quiescent current for the transistor. Moreover, viewed from the base or gate of the amplifier transistor (Q1), the impedance of the base/emitter or gate/source circuit is small at low frequency, and large with respect to the impedance of the radio frequency source within the radio frequency range of the signal. The device can be incorporated in a mobile terminal, such as a cellular mobile phone.
Abstract:
A transconductance stage includes at least one principal bipolar transistor having a base linked to an input terminal, a collector linked to an output terminal, and an emitter linked to a supply terminal through a resistor. At least one bipolar compensation transistor is connected in parallel to the principal transistor and linked without going through the resistor to the supply terminal. The value RE of the resistance is chosen so that RE*I0>VT/2, where VT is the thermal voltage and I0 is the quiescent current of the principal transistor.