METHODS AND APPARATUS FOR MICROPHONE PREAMPLIFICATION

摘要

Preamplifying circuitry amplifies sound signals for input into a computer system. A first stage common-emitter amplifier (16) provides high-gain amplification of the input signal, while a second stage amplifier (18) comprising an operational amplifier is suitable for driving a cable with the amplified sound signal. A low-cost constant voltage source (14) comprising a diode (26) and an operational amplifier (21a) supplies a voltage reference to both amplifier stages (16, 18) with a very high rejection of system noise. The circuitry and methods provide a low-cost, easily manufactured preamplifier suitable for sound input in desktop computing devices.