# After amplification of a signal through an amplifier

## Main Question or Discussion Point

hi....

after amplification of a signal through an amplifier, the amplified signal is 180 degrees out of phase with input..why??

thanks..

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Because it is an inverting amplifier? LOL

There are inverting and non-inverting amplifiers. If by "180 degrees out of phase", you mean that the output is "inverted", then you have an inverting amplifier.

Fish

vk6kro

It may mean you have an amplifier like this one:

This is missing a few important components, but it is OK to explain the principle.

If Vin is increased then the transistor conducts more and this makes the output voltage Vout decrease.

So an increase in input voltage produces a decrease in output voltage and a decrease in input signal produces an increase in output signal.

If the input signal was a sinewave, the output might be a larger sinewave but it would look upside down or 180 degrees out of phase compared with the input signal.