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Circuits > Audio > 3 Transistor Audio Amp (50 milliwatt)
3 Transistor Audio Amp (50 milliwatt)
Here is a little audio amplifier similar to what you might find in a small
transistor radio. The input stage is biased so that the supply voltage is
divided equally across the two complimentary output transistors which are
slightly biased in conduction by the diodes between the bases. A 3.3 ohm
resistor is used in series with the emitters of the output transistors to
stabilize the bias current so it doesn't change much with temperature or with
different transistors and diodes. As the bias current increases, the voltage
between the emitter and base decreases, thus reducing the conduction. Input
impedance is about 500 ohms and voltage gain is about 5 with an 8 ohm speaker
attached. The voltage swing on the speaker is about 2 volts without distorting
and power output is in the 50 milliwatt range. A higher supply voltage and the
addition of heat sinks to the output transistors would provide more power.
Circuit draws about 30 milliamps from a 9 volt supply.
3 Transistor Audio Amp circuit
Title: 3 Transistor Audio Amp (50 milliwatt)
Source: unknown
Published on: 2007-07-21
Reads: 1052
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