Sorry to be so technical. I think it would help those wanting to respond if you
stated exactly what your desire as your end product will be. Obviously the quick

answer would be an audio amplifier, but I have seen people wanting something a
little more specific as far as bandwidth and distortion.

Yes, a transistor, be it bipolar or fet will amplify but you have to bias it
properly. You just can't just use a single device transistor without all the
necessary biasing, protection, power output consideration, gain calculations,
and impedance matching. True, it is possible to provide what you need with only
one transistor or mosfet but biasing in the linear region could be complicated
or poor results will be obtained.

If your end product with the PIC and the driver is some sort of audio product,
distortion of your waveform should be less than 1% which means a good audio
amplifier module would suffice. Some that have responded on this list have been
helpful. If you can tolerate between 2 and 10% distortion similar to telephone
or two-way radio quality, then a simple amplifier, be it a transistor or op-amp,

and a follower circuit using a bipolar transistor could work, but you're talking

about "designing" an audio circuit.

If your supply voltage wanders between 9 and 16 volts, then a little more
elaborate regulator will be needed to keep your amplifier in the linear region.
Just remember, when working with audio, you're using linear devices that
transition somewhere a little below the supply voltage and a little above
ground, and not digital (on/off ) devices such as leds, relays, etc.

The last question is power output. Are you planning to drive a 1 inch speaker or

something that can be heard over a room full of people? A single 8 pin LM386
would probably meet your needs. Little more power, an LM380 (2 watts) will work.

That, and about 5 parts would be all you'd need. No real designing. Just follow
the datasheet. All parts available form Digikey or Jameco, ordered on line, and
cost per unit of parts would be less than $3.00 if placed on your project
circuit board.
There are lots of do-it-yourself kits from Jameco and a host of other kit
companies like
Hosfelt that includes the circuit board for around $10.00.

Hope this provides a little insight without getting too technical.

Good luck,

Rick



Max Peelman wrote:

> > In order to answer you question, a few parameters need to be known:
> > 1) What frequency, or what range of frequency are you planning to amplify?
> > 2) How much distortion can be tolerated?
> > 3) What amplitudes will you be generating, constant or varying?
> > 4) Will the sine wave ever reach DC or close to it?
> > 5) What peak to peak voltage is required on your load?
> > 6) Will it be AC or DC coupled to the load?
> >
> > Rick
> >
>
>     I'm sorry but I am only able to answer a couple of the questions
> myself as I just had the project dumped in my lap a day or two ago:
>
>     1) I'm not yet positive but somewhere in the range of 1-18 kHz
>     3) I don't plan to adjust the amplitude myself but it will be
>         dependent on the battery voltage supplied, somewhere in the
>         range of 9-16Vdc
>
>     I appreciate the leads on audio power amps and will investigate
> that option.
>     I am only familiar with transistors and FETs in relation to switching
> signals between a High and Low signal. Am I correct in assuming that
> I cannot amplify a Sine Wave signal using transistors or FETs?
>
>     Thanks again for the replies,
>
>     Max Peelman
>
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