I need to design a three stage amplifier with an undistorted output of at least 10 volt peak to peak. It must have a bandwidth from 20 Hz to 15 kHz, must be AC coupled, and have a voltage gain of 40 dB. I have to use transistors, FETS, or op amps. The output load must be 10 ohms, and i must use a 20 volt single sided power supply. I need help bad!!! Somebody Help Me Pleeeez!!!

 

Do you _have_ to design one or can you buy one? This sounds alot like audio amplifiers available from places like ST micro. Some have fixed gains around 32dB, some adjustable (to get 40), all are designed to drive 8 or 4 Ohms loads and all are designed fro low distortion in audio band. Many of them also run off a single supply (maybe up to 20V) using a mid-supply reference topology.

If you _have_ to design one, I would say forget about transistors for the amplifier stage you can do this with opamps & use power transistors for the output stage to drive your 10 Ohms. This can probably be done in 2 stages... so why must it be 3? gain of 40dB is do-able in 1 stage. For a good toplogy to get you started, take a look at the audio amplifiers I mentioned, you can do the same thing with opamps & power transistors.

 

Thnx for the help. I must design it. It doesnt have to be an audio amplifier. I wish i could buy one. It must be three because my teacher said it must be a three stage amplifier, that it about the only reason.

 

He said i must turn in: schematics, DC circuit analysis for all 3 stages including DC load lines and Q- points where applicable, AC circuit analysis for all 3 stages including AC load lines where applicable, calculated bandwidth for each stage, measured bandwidth for each stage, calculated gain at each stage as well as overall gain, and measured gain at each stage and compare to calculated values.

 

How much are you will ing to pay?

Do your own college work!

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To be fair, I might assume that tonyk is looking for help getting started - and is willing to do the work. If tonyk is asking for others to provide "schematics, DC circuit analysis for all 3 stages including DC load lines and Q- points where applicable, AC circuit analysis for all 3 stages ...etc etc" - that would be like an athelete asking someone to attend practice, do the workouts, etc - with the athelete expecting to compete when the time comes.

If it's the former - that you need some guidance - share some more with us.

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stevez

 

well here is only one possibilty for a start... a simple block diagram that shows what is going into each stage.

[Input stage] -> [gain stage] -> [output driver stage]

If you choose to use opamps, this may simplify your calculations if you are allowed to use the ideal properties due to high open loop gain.

Now, fill in the design and try to perform the analysis. post back with questions.

 

Read it. It is on the top of this forums.

 

I think he should start the electronics course all over again and actually go to each class. He doesn't have a clue about designing a simple amplifier's circuit.

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Uncle $crooge

 

So?

Like it says we will provide assistance, it doesn'tsay that we'll do college work or even projects for you.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

10Vpp outputs at 20V supplies is impossible, you need at least 22V supplies. Otherwise, use digital amp design. the digital design is possible to boost the voltage outputs, but worst distortion and emp.

 

16V p-p is easy if you use complementary emitter-followers on the output.
The driver's load resistor could be bootstrapped for a high output level.

Attached Images

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Uncle $crooge

 

Oh.. sorry that was 10Vpp outputs, there was +-10Vout in my mind.
My thanks to audioguru, for my mistakes.

Yes, its simple, you can use any conventional design.
Differential input stage -- Voltage amplifier --- Current amplifier. If that you mean with "three stage". 15KHz, 10Vpp @10Ohm isn't difficult. No need special components.

 

Oh... sorry, that was 10Vpp out, n there is +/-10V in my mind.
My thanks to Audioguru, for my mistakes.

 

Blatman, have any idea how old the thread is? Just thought you might want to notice..
I think the OP is onto bigger & louder things by now.