How to make constant gain amplifier circuit


Disabled Account
2004-11-14 7:10 am
I want to design constant gain amplifier circuit from standard transistor amplifier and not use negative feedback.

This amplifier must be run in class-ab is it posible ?

Constant gain amplifier can explain so easy such as ... 20log Vo/Vi = 30dB at every input voltage & every frequency & every speaker.

Can it's use electronic circuit or digital circuit for control gain ?

notice : this constant gain amplifier circuit will be insert between output of amplifier & feedback input stage



2005-02-11 1:25 pm
It is practically impossible to build an amplifier of almost any kind without some sort of feedback - at the very least, local feedback. If you are asking for an amplifier run in class AB without global feedback, this is actually quite simple. There are several mentioned on this site.
Electonic gain control should be possible though it may get complicated.
Now why would you want to insert an amplifier between an output of another amplifier and it's feedback node is something I don't understand - the net result will be an amp with attenuation and not amplification (-30dB attenuation)?
aht said: every input voltage...
By this I take it you mean high linearity, i.e. low distortion?

aht said:
...& every frequency...
You can't have constant gain at every frequency. Frequency response can extend down to DC, but it can't extend up to infinity; there must be a limit somewhere. If you need extremely wide bandwidth then it will mean compromises in other areas, such as reduced linearity or gain.

aht said:
...& every speaker.
Insensitivity to load, I take it this means. That's not too hard. Just keep the output impedance as low as possible and pay careful attention to stability.

You should note that all of these characteristics will be improved by using negative feedback.


Disabled Account
2004-11-14 7:10 am
Excute me

1.Every frequency = 20 - 20000Hz
2.Every input voltage = not more than 2.2V (will be satulated)
3.Every speaker = 4 & 8 Ohms impedance from really work

Sory for my bad English ;)



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Are you trying to build a volume control, an amplifier or address a real world implementation of something you are studying like this:

"the stabilization problem of the class of continuous-time linear stochastic hybrid systems with Wiener process. The "H-inf"state feedback stabilization problem is treated."

(from the paper you mentioned).

This is the question you need to address before anyone has any idea what you are asking about. Ok?

FYI, if it pertains to the quote above, I have no clue at this point what the heck they are yammering about! :eek: :bigeyes:

_-_-bear :Pawprint:

PS. "Linear Amplifier" for "transciever" usually means an RF device and not suitable for audio frequencies regardless.