Monday, April 8, 2013

1W Stereo Amplifier With Voltage Regulators

A simple
stereo audio amplifier is built around two 7905 negative-voltage
regulators (IC1 and IC2) and a few discrete components. The circuit
will also work with other 79XX regulators if appropriate power supply
is used. Regulator IC 7905 works as an amplifier for the voltages
applied to common pin2 (Ground or GND). Also check the LM317 audio
amplifier, another interesting circuit.The minimal voltage drop over the
standard 7905 is around 2V and it depends on the output current.
Feedback resistors in the IC set the gain of the channel internally.
The amplifier is a class-A audio amplifier. The minimal applicable
value of R3 for the regulator 7905 is 8.2 to 10 ohms per 5W.

7905 1 Watt Audio Amplifier Schematic

1watt 7905 stereo amplifier circuit schematic
the required output current for LS1 is below 100 mA, the value of
resistor R3 can be 33 to 51 ohms per watt. The circuit works with any
load resistance (R3 in parallel with LS1 as the load) under the
condition that the regulator is not overloaded with current and power
dissipation. However, it is preferable to use a loudspeaker with a high
resistance (8 ohms, 16 ohms or more). The amplifier works well with
low-impedance headphones having a resistance of 24 to 32 ohms. The
voltage difference between the ground pin of 7905 and the output pin is
fixed internally.
S2 is the on/off switch. Switch S1 is for
mono/stereo selection. When switch S1 is closed, the amplifier works as
a two-way mono amplifier. If S1 is open, the amplifier works as a
stereo amplifier. If no input signal is applied, the DC voltage on the
output of the regulator 7905 should be around –5V, which depends to
some extent on the value of VR1. The maximum output current of 7905 can
be up to 1A and the maximum power dissipation is up to 15W. Mount the
regulator IC 7905 on a heat-sink with