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Please Help me urgently

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:

1=2E Amplitude of the input voltage may vary between 10 mVpp and 50 mVpp.

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.

3=2E Output impedance of the ampli=AFer should be smaller than 2 k=AD.

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...

Reply to
mavihot
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typically the input voltage is first amplified then rectified and filtered to a fluctuating DC which is used to control a VCA (voltage controlled amplifier)

these are commonly found in AM radio circuits.

Reply to
TimPerry

How much are you willing to pay?

Bill

-- Ferme le Bush

Reply to
Salmon Egg

Such a device is called a compressor.

Example here:

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and here

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The use of a 1 transistor amplifier represents a fairly stringent requirement. If it had a 2k collector load then it would have an output impedance of < 2k. A voltage gain of 100 must be possible.

Probably the gain adjusting element would have to be on the input to the amplifier to avoid it becoming overloaded, some sort of JFET or LDR element such as in the examples above.

You'd have to get the gain in the AGC feedback loop right. I think you'd have to build it to prove it, god only knows what the "gain" of an led and a LDR glued into a plastic tube is.

No.

The AGC in AM radios is driven by rectifying the carrier.

Rectifying the audio to drive the AGC could lead to distortion of various kinds and other undesirable effects, which is apparently what is required in the answer to this question. :-)

For this reason the use of compressors in broadcasting is avoided whenever possible.

See also:

DG

Reply to
Derek ^

it has the effect of maintaining audio levels as the signal strength fluctuates. i feel pointing the poster in the direction of commonly available radio AGC circuits may help provide an understanding of what is needed without actully doing classwork for him.

you are either joking or you have no idea about audio processing in broadcasting. compressors are used at every stage of the broadcast airchain starting with the mic preamp and more at the STL then finally whopping big AGC + compression + limiting at the excitors.

a form of AGC is even used to control power output in most modern broadcast transmitters.

Reply to
TimPerry

Probably not much, he is a student in a Turkish university....

Reply to
Adrian C

Suppose a student wanted, and maybe even needed, my house. How much of a price break should he expect?

Bill

-- Ferme le Bush

Reply to
Salmon Egg

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