An electronic circuit contains a controller integrated circuit and a power amplifier MMIC connected to the controller IC. The power amplifier MMIC contains a radio frequency power amplifier. The RF power amplifier is a double heterojunction bipolar transistor. The controller IC has an operational amplifier that supplies a DC bias to the base of the RF power amplifier through a ballast resistor. The operational amplifier has an output slope that compensates either partially or entirely for the voltage drop across the ballast resistor. A reference circuit in the power amplifier is disposed close enough to the power amplifier to mirror fluctuations in the base-emitter voltage caused by temperature fluctuations.

An apparatus and method for amplifying a radiofrequency (RF) signal. The apparatus comprises a control circuit including a first transistor, a second transistor, and a ballast resistor coupled between an emitter terminal of the first transistor and a base terminal of the second transistor, such that a control voltage applied to a base terminal of the first transistor controls the amplification of a signal applied to the base terminal of the second transistor. Additional elements may be coupled to the control circuit to improve the performance thereof, including a feedback stabilization circuit, a diode stack circuit, a bypass capacitor and an additional resistor.

An amplifier element amplifies RF signals. An emitter follower unit drives the amplifier element at a constant voltage corresponding to a reference voltage supplied to a reference terminal from outside. A current injection unit drives the amplifier element at a constant current corresponding to the reference voltage. An analog control unit analogically controls the output voltage of the emitter follower unit in correspondence with the control voltage supplied to a control terminal from outside. A mode switching unit switches whether the emitter follower unit is operated or not in correspondence with the control voltage.

A high-frequency amplifier has an amplifying transistor and a bias circuit that supplies a bias current to the base of the amplifier transistor. The bias circuit has a reference voltage input terminal to which a reference voltage is input from an external source, a first transistor that supplies a bias current to the base of the amplifier transistor in response to the reference voltage, a second transistor whose collector is connected to the connecting point of the first transistor to the base of the amplifying transistor, and whose emitter is grounded, a third transistor that supplies a bias current to the base of the second transistor in response to the reference voltage, and temperature compensation portions connected between the connecting point of the control input terminal to the third transistor and the grounding point.

A bias circuit includes a transistor having a control gate, a first terminal and a second terminal coupled to a ground level, a first resistor coupled to the control gate, a first capacitor coupled between an input signal and the first resistor, a diode coupled between a connection point of the first capacitor and the first resistor, and the ground level, a second capacitor coupled between the control gate and the ground level, a second resistor coupled between the control gate and the ground level, a third resistor coupled between the control gate and a predetermined voltage, a fourth resistor coupled between the predetermined voltage and the first terminal, and a fifth resistor coupled between the first terminal and a bias signal. A current through the transistor corresponds to the input signal, and the bias signal is generated according to the current through the transistor.