H-bridge

[epilot]

hello,

after looking at a H-bridge motor driver i thought to ask this question,

is this possible using a H-bridge circuit(probably based on transistors) as an audio amplifier for a speaker?
can it work perfectly?

 

[audioguru]

An H-bridge is digital, it switches its outputs on and off. An audio amplifier is linear, a small voltage input makes a small voltage output.
Therefore if an H-bridge was used as an audio amplifier then the sound would be just nothing or square-waves.

You might be able to use an H-bridge as a Class-D amplifier, that uses Pulse-Width-Modulation and switches at a very high frequency.

 

[hjames]

If you look at the output transistors of the two opamps arranged in a "bridged speaker" configuration, you'll notice that they look just like a H-bridge. There isn't anything particularly special about H-bridges - just add an opamp to linearize each side, and you'll see the power dissipation associated with linear amps, and the speaker will see a larger voltage swing across it.

If you want to the class D amplifier that audioguru mentioned, that'll probably be a bit trickier.

 

[Styx]

yes you can and they sell. In fact the amp in yr MP3 player or phone is a H-bridge audio amp. Or as it is also know a Class-D amplifier NOTE the 'D' does not stand for digital

The switching freq is in the order of a few 100kHz and there is extra filtering on the output to clean up any distortion due to the switching

 

[audioguru]

The switching freq is in the order of a few 100kHz and there is extra filtering on the output to clean up any distortion due to the switching

The filter is to reduce the level of the switching frequency across the speaker so that without any sound, the efficiency is much higher. Without a filter, the speaker is a load for the switching frequency which wastes power.