This low-power solution makes use of Sanyo integrated circuits that are also found in commercial equipment, so easy to obtain in the spare parts market. Radios, recorders and other small and medium power sound equipment make use of these ICs.
The LA4120 provides a power of 1 W in simple 4-ohm 6-ohm monaural configuration. The LA4125 provides 2.4 W of 4-ohm with 9 V and the LA125T reaches 4.2 W of 4-ohm load with 12 V.
In figure 1 we have the complete diagram of the amplifier, observing that we have two channels of amplification.
In figure 2 we have the printed circuit board for the assembly, observing the large copper area that is left on purpose to function as a heatsink and as shielded ground circuit.
Typical quiescent currents range from 35 to 45 mA and the typical voltage gain is around 50. The typical input resistance is 30 k ohms.
MATERIAL LIST
Semiconductors:
CI-1 - LA4120, 4125 or 25T - integrated circuit
Capacitors:
C1, C2, C3, C4, C9 x 10 V - electrolytic
C5, C6-150 nF - polyester film
C7, C8 - 470 uF x 16 V - electrolytic
C10 - 1000 uF x 16 V - electrolytic
Several:
Printed circuit board, wires, solder, etc.
