ABSTRACT
This chapter covers the solid-state audio lines-stage amplifier design. The voltage gain of a line-stage amplifier often ranges from 5 to 10. In addition to the voltage gain, wide bandwidth (> 100kHz), low distortion (< 0.01%), and high signal-to-noise ratio (> 90dB) are also required for a good line-stage amplifier. Most line-stage amplifiers discussed in this chapter can easily meet these requirements. The discussion starts with a conventional three-stage line-stage amplifier employing a cascode differential amplifier input stage, cascode amplifier second stage, and double-emitter follower (Darlington) push–pull output stage. Then the design is developed into employing different amplifier configurations with a complementary cascode differential amplifier input stage, complementary cascode push–pull second stage, and diamond buffer amplifier output stage. The topology of the line-stage amplifier evolves from unbalanced input-unbalanced output into fully balanced. The solid-state devices used in the design include BJT, JFET, MOSFET and op-amp. Finally, various types of potentiometers for volume control are discussed. They include rotary, motorized, stepped attenuator, and digitally control potentiometers.
