1OW audio power amplifier circuit using UPC1238

The circuit uses the integrated amplifier μPCI238 as the amplifier device. The input signal is added to the in-phase input terminal (pin 1) of the operational amplifier through the coupling capacitor (its capacity is 1μF) and the resistor (its resistance is 56kΩ). The 56kΩ feedback resistor R1 is connected between its output terminal (pin 4) and the inverting input terminal (pin 2), and the 1kΩ resistor R2 and 22μF capacitor are connected between the inverting input terminal and the ground. The voltage amplification factor of this circuit is: Av=(1+R1／R2)≈(1+56／1)=57 times. μPCI238 has excellent performance and is powered by a ±13V power supply voltage. Decoupling capacitors (100μF and 0.1μF in parallel) are connected between the positive and negative power supply terminals (pins 5 and 3) and the ground. 100μF is a large-capacity electrolytic capacitor and 0.1μF is an organic film capacitor. The output terminal (pin 4) is externally connected to a high-frequency suppression circuit (a 3Ω resistor and a 0.22μF capacitor in series) and an 8Ω equivalent load (speaker).