The circuit posted here is of preamplifier and is simplest possible. This circuit provides a voltage gain of about 3 to 30 and is depend upon source and load impedance. The circuit simple preamplifier has low input impedance.
Circuit Description of Simple Preamplifier
The circuit of simple preamplifier is designed using a single low power amplifier transistor and is configured in common emitter mode. The input signal is given to the base of transistor T1 through capacitor C1. Capacitor C1 is a coupling capacitor to couple the input signal to the base-to emitter terminals of the transistor.
Vcc of 12V is given to collector which serves the additional function of providing the base current. Under zero signal condition capacitor C1 acts as an open circuit since the reactance of capacitor is infinity at zero frequency. Thus, the capacitor C1 acts as blocking capacitor. Similarly capacitor C2 serves the same function. Thus capacitor C2 works as coupling capacitor and feeds the amplified signal to constitute the output voltage.
The circuit simple preamplifier uses fixed bias. In this circuit, the zero signal operation may be established by selecting resistance R1.
PARTS LIST OF SIMPLE PREAMPLIFIER
|Resistor (all ¼-watt, ± 5% Carbon)|
|R1 = 2.2 MΩR2 = 4.7 KΩ|
|C1, C2 = 10 µF/10V|
|T1 = BC148B|