# distorted output in class A audio amplifier

#### alimash

Joined Oct 12, 2016
67
hey friends
i am building my first class A audio amplifier
i achieved the dc biasing step successfully
this is my circuit:

the problem is when i connect the audio signal to the output i get a distorted signal
output signal:

i can not figure out why
what am i missing here
thank you

#### R!f@@

Joined Apr 2, 2009
9,916
May be too much input.
Decrease the input AC voltage and check.

#### AlbertHall

Joined Jun 4, 2014
12,328
Your input voltage is too big and the amplifier is limiting. Try it with a 10mV input.

#### alimash

Joined Oct 12, 2016
67
it works thank you guys,
but why this is happening?

#### R!f@@

Joined Apr 2, 2009
9,916
Too much input distorts the input, hence the output too.

#### AlbertHall

Joined Jun 4, 2014
12,328
Look at the input and output voltages you now have. The output voltage divided by the input voltage gives you the gain of your amplifier. Your original circuit had a 1V input so multiply that by the gain and that is the output voltage your circuit was trying to produce but it only has a 12V supply voltage.

#### dannyf

Joined Sep 13, 2015
2,197

#### alimash

Joined Oct 12, 2016
67
wow that is intense
thanks
it is all clear now
cheer

#### Bordodynov

Joined May 20, 2015
3,164
Last edited:

#### Veracohr

Joined Jan 3, 2011
772
C3 is bypassing the emitter resistor so the emitter resistance for AC is only about 25 ohms (25mV/1mA). The gain is then 6800/25=272. Too much for the input/power supply voltage.

#### joeyd999

Joined Jun 6, 2011
5,162

#### BobTPH

Joined Jun 5, 2013
8,654
Well, you fix works, if what you want is an amp with a gain of 4.

There was nothing wrong with the original circuit. It is just that it had too much gain for the input signal you were giving it. If you had reduced the input signal as suggested it would have worked as well.

Bob

#### Wendy

Joined Mar 24, 2008
23,396
My 2cents ,too much gainin the circuit.Look closely at the emitter capacitor. It is boosting your gain to max,