Transistor selection. SS amp designers please read. Thank you!

[Frazzled]

The one BIG question I have always had about amplifier design is how designers pick transistors, is there some sort of magical reference guide that they have or after a while do designers come to have favorite transistors for certain stages of amplifier design that they like to use. Also I have noticed a kind of regional flavor to amplifier design in that certain part numbers show up more often in say Australia than they do in North America.

Also an amplifier I am trying to get working makes use of one IRF9610. Do you know I tried for two years to purchase these from local suppliers (READ NON INTERNET OR CATALOGUE SUPPLIERS) but do you think any of them stocked this transistor, yet they seem to be growing on trees in some places. I used an IRF9620 instead because this is what I could get my hands on.

On a side note if any of you guys have 10 to 20 IRF9610's kicking around I would love to buy them, I can pay you with PayPal right now.

Anyway I hope somebody can shed a little light on this subject, perhaps Mr. Pass would be so kind as to chime in.

Thanks for your time everyone.

Oh and if anyone would like to see the amplifier I have been trying to get working it all is well documented and starts HERE in this thread.

[destroyer X]

They informed us where the transistor are linear and were not.
This way, you could make better choice.... the one to drain maximum 5 amperes, with VCE of 40 volts, and theres the correct input current to be exactly in the middle of the straigth line, where linear operation happened.

Now a days, i cannot have those informs anymore, this way, i am having those informs researching the professional amplifiers donne..... and taking notes of the correct complementary pairs, the working voltage, the working output maximum current and sometimes, when circuit is strange, i calculate the input current and voltage too.

New times, new world, almost everything done related developments, time to copy... at least, i am doing that.

regards,

Carlos

[EnvisionAudio]

On a side note if any of you guys have 10 to 20 IRF9610's kicking around I would love to buy them, I can pay you with PayPal right now.

Anyway I hope somebody can shed a little light on this subject, perhaps Mr. Pass would be so kind as to chime in.

Thanks for your time everyone.

Oh and if anyone would like to see the amplifier I have been trying to get working it all is well documented and starts HERE in this thread.

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

Try those. I'm sorry your amplifier has been documented so poorly. I have never built the AV800, but find your problems dicsconcerting...especially for a "kit" type project.

[Frazzled]

Thanks.

Actually that is me bidding on those IRF9610's

I am a little saddened by the state of this amp too, but as I have stated it is forcing me to learn more about amplifier design and that is a good thing!

[cunningham]

If you want to design an amplifier circuit, I would recomend starting with a scematic drawing and not a pre-manufactured board designed for another circuit. Start with a topology that works by general design then work out the math involved to solve the circuit to use any changes and circuit upgrades you may make in the topology and componant changes. I like to use the parts that I already have to save money on account of I don't have very much.

Construct the circuit on a bread board(protoboard or whatever you call it) anyway, you can make changes to the circuit with relative ease. When you have a circuit that performs the way you want, then design the PCB to fit it and make it yourself... Etching

BTW: You can overdesign to use cheaper more available parts, but it may not be as effiecent. Basically design the circuit so that the circuit operation is not specifically related to the individual componant specs so that circuit operation doesn't change when transistors are replaced with a similar device.