Amplifier IC selection

Ahh probably should clarify I'm not after a whole circuit design just a suitable amplifier IC for the job, I can do the design (I hope)... :)

is cheap, readily available and easy to work with. Its used in "gainclone" audio power amplifiers by a legion of audio DIYers.

Glenn.

"glenbadd" Adam

** Delivering 26 volts rms ( +/- 37 volts peak) into even a tame load will stress the LM3886 to its limit.

The DC supply used will have to be +/- 40 volts under load and have very little 100Hz ripple - also, it must not go above +/- 45 volts of the chip will fry.

The OP must say what the load is ( a Piezo driver ? ) or there is no way to be sure it will work OK.

....... Phil

It's driving a Resolver, the Sin & Cos outputs of the resolver are fed into a Resolver to Digital Converter Card for which I have no input impedance information. I know that 10W is heaps of headroom. I suspect the input impedance is in the mid to upper kOhm range but can't be sure.

I have +24 and -24 rails available so it'd be nice to stick within these. Hence the step up Transformer on the output.

Is the '10W' based on a guess, or a firm knowledge of what load ipedence you are hoping to drive ?

geoff

Yeah 10W was more so I can derate the IC and not have to stick a big heatsink on it. Appologies for the confusion so far.

"Adam"

** Not everyone is into "robotics" or servo control systems - Adam.

For the uninitiated:

** Use the LM3886 and step up the output voltage with a transformer.

A 15 volt, 1 amp multitapped, 2155 type should be OK.

Just use the secondary as a 1:2 step up autotransformer and trim off and insulate the primary wires.

...... Phil

woops my bad.

woohoo thanks Phil. It looks like a good chip. I'll lurk in here and offer some help back now that i've got a news reader set up again.

Excellent Idea. Slightly off topic, I also have a need to amplify a sinewave, but 3 phase 70hz, about 20v pk. Its from a turbine tachometer generator with 3 phase output to drive a 3 phase tachometer indicator (gauge). The reason I need to amplify the signals is because the gauge reads a bit low. Would 3 step up transformers work ok?

If you mean 'amplify' in terms of provide more available power, then no, transformers won't work. If it's a case of there's excess power available, but the voltage is too low, then they may, depending on the numbers. 3 transformers, one per phase with star points commoned on each side.

On Wed, 07 Nov 2007 13:09:00 +1100, Adam put finger to keyboard and composed:

What about a hybrid stereo audio amp, eg something in the STK series? I've seen these with +/-30V, 40W ratings. Of course they're designed for 4 or 8 ohm loads, but I can't foresee any problems driving into a few Kohm, if that is indeed your load impedance. The cost should be of the order of $15 - $25 (from WES).

- Franc Zabkar

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