# Necessary steps to design Mini Audio Amplifier Circuit With BC547

#### Audioguru again

Joined Oct 21, 2019
1,727
I wrongly calculated the p-p voltage for 25mW, not 20mW.

The peak voltage is half the peak-to-peak voltage. The peak voltage is 1.414 (the root of 2) times the RMS voltage. The peak-to-peak voltage is 2 x 1.414 times the RMS voltage. 2 x 1.414 is 2.828.

#### anhnha

Joined Apr 19, 2012
881
Okay, let's assume that the output power is 5mW
how do you calculate the component values?

#### Bordodynov

Joined May 20, 2015
2,642
Here is a power of 29 mW at a supply voltage of 3 V and thus small distortions. Signal amplitude at 15 mV input, 1.36 V output amplitude. As output transistors I took transistors with low saturation voltage and increased power dissipation.

#### Audioguru again

Joined Oct 21, 2019
1,727
Many people want the loudest peak power of music into their earbuds or earphones to be 20mW at low distortion, but some headphones will be louder and others will be less loud. Your assumption of 5mW is probably not loud enough. It might be like faint background music. In Google, look up Cmoy Headphone Amplifier that uses modern opamps, not old-fashioned discrete transistors.