1 to 2W audio power amplifier for easy in-instrument installation

The internal equivalent circuit of LM3 8-ON and the connection of the input circuit
are similar to the PNP differential amplification method. When using a single power supply, the output stage
consists of a SEPP output circuit, and the transistors are equivalent to PNP power tubes.
    Because there is no internal feedback, the voltage amplification is fixed at 50 times (34dB).
At the same time, due to the high input level , a variable resistor is added to the input end to widen the
input level range. The power supply noise suppression of LM380N is relatively poor. , so
the AC filter electrical gap 1 is connected in series to the bias current lead (BP).