LA4550 Audio Amplifier 4W BTL.

LA4550 is a 2 channel audio frequency power amplifier IC specifically designed for radio, tape-recorder use etc. The features of LA4550 are low quiescent current, built in 2 channels for stereo and bridge mode operation, excellent ripple rejection, good channel separation, negligible pop-up noise during power ON/OFF. The LA4550 can be operated from 12 Vdc and can deliver 4W of output power into an 8 ohm speaker.


In this circuit LA4550 is wired in bridge mode. For stereo application, two identical amplifier modes have to be built according to the circuit diagram. In the circuit capacitors C6 and C3 provides feedback and their value determines the lower cut-off frequency. Capacitors C1 and C7 are meant for bootstrapping. Branch C2, R1 and C8, R3 are meant for preventing oscillations, and so the high frequency stability of the LA4550 audio amplifier gets improved. Capacitors C9 and C10 are meant for coupling the speaker to the IC. C4 is a ripple filtering capacitor while C11 and C12 are meant for power supply filtering. Audio input can be applied to pin 8 of the IC with respect to the ground.

Circuit diagram.

audio amplifier LA4550
LA4550 audio amplifier circuit.


• Use 12 Vdc for powering the circuit.
• Maximum possible supply voltage is 13V.
• LA4550 requires a heat sink.
• The package style of LA4550 is DIP 12F and suitable heat sinks are available in the market.
• Use 8 ohm/10W as the loudspeaker.
• An optional 10K POT connected in series to the input line can be used as the volume control.


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