# Multi-stage digitally controlled variable amplifier design

#### BuMalak

Joined Oct 12, 2012
17
Hi all,

The design problem is:
Design A multi-stage digitally controlled variable amplifier with a gain range of 50 to 200 with a step of 50.

You should be able to:

A) Amplify the center frequency, which is equal to (3kHz), input signal with four different digitally controlled gain steps.
B) Attenuate out of band frequencies from 1kHz to 3kHz, by 20 dB.

#### kubeek

Joined Sep 20, 2005
5,796
Looks like a homework to me, but anyway..
What kind parts are you allowed to use? Can you use analog switch ICs, or does it have to be made out of discrete parts? Are you gonna make the circuit in physical form, or just a simulation, or just a diagram?
Do you have a basic idea how the circuit should work?

So many questions, so little input on your side..

#### BuMalak

Joined Oct 12, 2012
17
I am allowed to use analog and digital IC.
and I have to design, simulate, and make the circuit in physical form "implement it".

#### kubeek

Joined Sep 20, 2005
5,796
I hate to repeat myself, but
"Do you have a basic idea how the circuit should work?"
Or do you expect someone to do your work for you? The way I see it, you should be the one asking the questions, not me.

#### BuMalak

Joined Oct 12, 2012
17
I myself do not know how to start
can you help?
I do not want you to do all the work, but hints and ideas may help.
Thank you.

#### kubeek

Joined Sep 20, 2005
5,796
From the requirements you posted you will need these circuit blocks:
1x band-pass filter
4x amplifier with gain of 50
3x analog switch to bypass three of the amplification stages

But still the A and B requirements seem to contradict themself, if you have something called center frequency, then I think you would want to attenuate anything around that, so that for example the band from 1khz to 6khz stays: You should ask your supervisor about that, or provide some explanation that makes more sense.

With a little bit of thinking you should be able to draw a block diagram from the building blocks, so that the circuit overall achieves what you´re being asked.