BS in Electrical Engineering
Electrical Engineering Department
There is a need for linear, efficient monolithic power amplifiers used for the wireless transmission of signals with amplitude variations. This paper proposes a circuit that actively biases a bipolar transistor so that it operates as a Class C amplifier, with a conduction angle that is constant over a range of output powers. This results in a linear amplifier with a very low two tone intermodulation distortion. By forcing a scaled DC current vs. input magnitude curve from a Class B amplifier on to a Class C amplifier, a constant conduction angle can be maintained in the Class C amplifier. The effect of, and compensation for, a knee in the current voltage characteristics of an amplifier is simulated and analyzed. The tuning of a sweet spot in the two tone intermodulation of an amplifier is addressed. A linear constant conduction angle amplifier with a minimum two tone intermodulation distortion of -53.9 dBc and conduction angle of 137 degrees is presented.