Please Help me urgently

If you're waiting for us to do your homework for you, you're going to be waiting quite awhile. On the other hand, if you've had a good try at it and are just stuck on one or two things, your odds are better. Posting from a real email account (not Gmail or hotmail) will improve your odds further.

What have you actually done so far?

Cheers,

Phil Hobbs

try posting to sci.electronics.homework

martin

Hello, I can not handle a problem which is about AGC. Please help me about that. The conditions are; It is required to design and implement an AGC circuit with the following specifcations:

2=2E Amplitude of the output voltage should be in the range 0.9 Vpp and1.1 V pp for the input signals with amplitudes stated above.

4=2E The circuit should be able to amplify the signals having frequencies

between 500 Hz and 10000 Hz.

The amplifer designed should be a single transistor amplifer in the common-emitter form for BJT amplifers or common-source form for the FET amplifers. However, it can be used extra transistors for making the

amplifer an adjustable gain amplifer.

And the AGC should be composed of 2 parts adjustable gain part and feedback part.

Please help me urgently to design this problem. Thanks...

Hello, thanks to response my problem. I have spent a lot of time for this problem, but I can not find a specific solution. I used a BJT for amplification. Then connect a resistor to input, then I connect a JFET other terminal of the resistor. And connect the JFET to the output. I use JFET by using its property of it is a voltage controlled resistor. By using this property and making a voltage division there. I adjust the outout to neighbourhood of 1 Vpp. However one of the problem is that I can not get a proper output, also the output is AC signal, but I have to control JFET DC signal; this is one of the problem. I thought that I can use a full wave rectifier to change AC signal to DC signal, unfortunately I am working about 1 V , and diodes opening voltage is about 0.7 V; so, it is not a proper way. If you give me your e-mail address, I can send you our Multisim Simulation for this homework, because I have worked a lot on it. Finally, the most important problem is whether I am on the right way or not. This is very important. My finals just finished and I have not had much time for this work. Please help to design this work. If it is possible, I will be pleased about that. Thanks for your interests

Hello, Thanks, but I can not send it to sci.electronics.homework Could you help me how can I send it? Thanks again.

Hint #1: for low distortion, keep the AC voltage across the JFET used to control the gain as low as you reasonably can.

Hint #2: Have that JFET handle AC only, no DC, in order to offer a reasonably linear resistance.

Hint #3: With a high load impedance, silicon diodes conduct enough to offer significant rectification much below 0.7 volts.

Consider other topologies than you have so far. For example, consider using the FET and a resistor to form a voltage divider, which then feeds an amplifier stage. There are many ways you can solve this problem. Don't invest too heavily in just one at first. Step back from the problem and think of some different ways to do it, and then weigh the pros and cons of each.

More later, after you mull that over.

Cheers, Tom

I love it!

Bob

Just to make explicit what others did not...

"sci.electronics.homework" does not exist.

In these forums, people are very unwilling to do students' homework for them. Also, remember that your teacher may be here, too.

Design consultancy is easy to obtain. It involves paying money though.

Graham

Read fast:

Good Luck! Rich

Also, apply some of the drain's AC voltage to the gate. You want to bring the change of the RDS(on) with AC voltage near to zero.