A High Gain Medium Power Audio Amplifier Circuit

Abstract

In this proposed work, a high gain and medium power discrete audio amplifier utilizing a class-AB output stage is designed and simulated. The audio amplifier uses discrete active devices such as BJTs and JFETs. It consists of a pre-amplification stage, tone control circuit and class-AB complementary-symmetry output stage. Due to their high input impedance, JFETs are used at the input side of the audio amplifier. The remaining part of the amplifier circuit uses BJTs operated in active region. A miller capacitance is connected to vary the bandwidth of the circuit. Since single stage amplifiers exhibit limited gain, the proposed audio amplifier incorporates multiple stages with miller capacitance. The design was carried out assuming a set of general specifications and simulated using Microwind software. The circuit is powered from a ±10V power supply and the power consumption is found to be 946mW. The measured 3-dB frequencies were found near to the audio frequency range (48Hz to 22.5 KHz). The total harmonic distortion (THD) is measured to be 5.4%, while the responses of input resistance and output resistance versus frequency curves have been simulated.