Patent attributes
A general purpose Darlington pair amplifier circuit, configured in accordance with a preferred embodiment of the invention, utilizes GaAs heterojunction bipolar transistor technology. The amplifier circuit incorporates a temperature compensation circuit at the input stage that controls the total current drawn by the transistors such that the total current is stable over temperature. The temperature compensation circuit includes a feedback resistance element and a bias resistance element that form a voltage divider that establishes the base voltage (bias voltage) of an input transistor. The feedback resistance element and the bias resistance element are of different types, having different positive temperature coefficients. In the example embodiment, the temperature coefficient of the feedback resistance element is greater than the temperature coefficient of the bias resistance element. The difference in the temperature coefficients compensates for the negative temperature coefficient of the base-emitter turn-on voltage of the transistors employed by the amplifier circuit.
