DESIGN OF A TWO-CHANNEL SOLID-STATE一个双通道固态设计_精品.doc

1. Introduction The project involved designing and constructing a high-fidelity Class-A amplifier. Design was solid-state based and biased with a constant current source in a push-pull configuration. The final product is to be compatible for use with any conventional audio input, which has been pre-amplified, and output is to be coupled through conventional 8( speakers. The choice of solid-state over vacuum tubes is largely because solid-state amplifiers are more dynamic in nature, and are hence better able to amplify frequencies in the low to mid-range, and because solid-state amplifiers are more cost effective and have lower maintenance costs than their counterparts. Overview of Output Classifications Output stages of amplifiers are classified according to the standards shown in Table 1.1. Table 1.1 Classification of Output Stages Class Definition A Linear operation with 360( operation of a sine wave. Operating point is set at about the center of the operating range and in operation, the output signal produces approximately equal excursions towards the two axes B Transistors are biased to cut-off, such that only 180( conduction can occur. “Push-pull” operation is necessary with each half of the output amplifier alternately supplying the two halves of the output signal. AB Small forward bias and output stages are not completely cut-off. C Stage is biased beyond cut-off, allowing less than 180( conduction. 1.2 Class-A Operation Class-A generally offers the lowest distortion among the output classes and since high fidelity and low distortion is desired for this project, the design is based on Class-A operation. The primary virtue of Class-A lies in the smooth characteristics of its operation parameters. The gain transistors are operated in the linear region only, where distortions are limited to smooth, simple forms, unlike abrupt distortions created in Class-B amplifiers when the transistors switch on and off. In Class-A operation, transistors are always on,