Micro-Amplifier Based on LM4780

Overview

The project was based on LM4780 IC which is a 60W stereo power amplifier in order to produce the micro-amplifier.

Explanation

Two boxes comprise the design where one is used for the main amplifier and the other for power supply. A thermal shutdown feature is also included in the design. The 3 distinct sections of the circuit include a temperature sensing circuit, an LED flasher, and a power supply, which are tightly integrated resulting in a low component count. The sensor is a classic 2-transistor Schmitt trigger where TR2 switches the mute current directly. The mute switch is wired across the thermistor and when activated, it simply shorts out the device simulating a gross over-temperature situation, making the audio muted.  This is one of only two components in the whole design that sees the whole supply voltage of 50-60V.

The LED flasher is the final section where the two transistors form the classic 2-terminal flasher circuit which is normally placed in series with a load although the circuit can also be placed in parallel with the load. A tiny operating current is required by the circuit which measures in mA and rises to around 3mA.