ABSTRACT
Megaphone is very common life of a class of electronic products, the
use of it is very extensive. Amplifier circuit is put the faint sound
amplification can push into the high-powered signal, circuit structure
is mainly divided into the preamplifier, tone control two parts.
Preamplifier main perform small signal amplifier, general
requirement high input impedance, output impedance low, wide frequency
band, the noise is small. In the design of preamplifier level are divided
into two levels, the first level for common source amplifier circuit, the
whole circuit amplification depend mainly on the first level; The second
grade level is shot with, ensure tone control circuit has good effect,
to the tone control circuit with a small signal source resistance. Tone
control mainly is the realization of the input signal is high, the bass
ascension and attenuation; Due to the integrated operational amplifier
has voltage gain high input impedance, higher advantages, and use it to
make the tone of the control circuit has simple structure, stable circuit,
etc.