# How to calculate value of each component in an audio amplifier

Tda 2030a is a 19W audio amplifier. I have connected a 25W 4ohm subwoofer to it. I have done the soldering and the circuit is working successfully but I want to understand the working and the calculation behind each component. The diagram is from the datasheet of the respective opamp of the company. The link is attached below.

I want to know why there is a potential divider at the start (fig 1) and the gain of the opamp consist of resistor in series with capacitor (fig 2) and the fig 3 doesn't make any sense to me to all.

I also want to know the calculations behind all of this. I know for sure that all of this has been done to reduce noise and improve gain but I do not understand how exactly everything is working.Can anyone help me ?!! Thank you so much for your contribution!!

Datasheet link: Tda2030a

• The TDA2030 is not an opamp. It is a power amplifier. – JRE Mar 27 '18 at 13:30

## 1 Answer

The components in group #1 (plus the resistor immediately above) are biasing the amplifier to half the supply voltage, since it is being used with a single power supply.

The components in group #2 set the gain of the amplifier. The capacitor provides a low-frequency rolloff, making the DC gain unity. The corner frequency is

$$\frac{1}{2\pi R C} = 15.4 Hz$$

The components in group #3 are there to interact with the output impedance of the amplifier (and the inductance of the speaker) in a way that improves stability. The datasheet is not particularly forthcoming on this topic, but the comments in Table 7 offer some clues.

• A google of zobel network may help with group 3. – Colin Mar 27 '18 at 13:37