Gain less than unity using TPA4860 1W audio amplifier

andre.robotokogaku

Other Parts Discussed in Thread: TPA4860

Hello there guys,

Could anyone tell if it is possible to have a amplifier with gain less than unity? Specifically, if TPA4860 allows gains smaller than 1?

In my application, I'm driving a speaker (8ohm) to play alarms. To generate the sound, I'm using a MCU output and basic square wave generation. The sound waveform does not matter as it will work as a beeper only, but will have different frequencies and a volume control.

I'm also using a digital potentiometer to control the gain resistor Rf of TPA4860.

The problem is that the amplifier's output saturates even with gain equal to 1. My MCU is a MSP430, so it is running with 3.3V. The TPA4860 is powered with 5V.

Thanks in advance,

André.

over 13 years ago

0 Neil Albaugh over 13 years ago

Genius 5430 points

Andre;

A voltage divider should work.

0 andre.robotokogaku over 13 years ago in reply to Neil Albaugh

Intellectual 440 points

Neil and everyone,

Indeed, the divider worked. Also, with appropriate resistor values it was possible to achieve gain smaller than one.

Actually I didn’t find out what was the problem. I decided to remove all audio components and assemble again (using new components).

It worked fine, except I’m experiencing an annoying noise (3.6 kHz) coming from the speaker when there’s no audio.

It’s now time to move on and solve this new issue!

Thanks,

André.

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Gain less than unity using TPA4860 1W audio amplifier