# Instrumentational Amplifier

Discussion in 'Electronic Basics' started by tuurbo46, Apr 13, 2004.

1. ### tuurbo46Guest

Hi

Im currently trying to alter the input impedance of an operational
amplifier, but cant find the right page on google. I think impedance
means, there must be an RC circuit in series with the amplifier? Does
anybody have any ideas?

2. ### Kevin AylwardGuest

Impedance is the net impediment to current. It can be a function of many
things. It is not exclusively the result of R's and C's.
Yes. Explain what problem you are trying to solve, don't ask questions
on your preconceived solution to the problem. From your post it is clear
that you don't understand impedance at all, i.e. what it even is. Since
this is the case, how do you know that you want to "alter the input
impedance of an operational amplifier" at all? Incidentally, this
statement makes no sense. You cant alter the input impedance of an
op-amp at all. You can only alter the impendence at a node that the
op-amp is connected to. The input impedance of an op-amp, is whatever it
is, usually Mohms.

Kevin Aylward

http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
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3. ### tuurbo46Guest

Hi

i will read my uni assignment again and i will get back to you with
the correct question!

Cheers Turbo46

4. ### tuurbo46Guest

The above question was in relation to one of my recent uni
assignments. The assignment was to design an Audio premaplifier
question. The part i didnt understand and still dont is how you
change the input impedance to an operational amplifier? I have
enclosed the question below:

Input 1: Design a low inpedance source(1.2k) balanced(i.e.
differential i/p plus ground).

At this point i choose the operational amplifier, but i was lost on
the input impedance part. My misusderstand was that impedance was AC
resistance, but i was wrong.

5. ### Rich GriseGuest

Howcome you can't ask your teacher? Isn't that what they're there for?

Good Luck,
Rich

6. ### JeffMGuest

Input 1: Design a low inpedance source(1.2k)
You're getting warm.
Cold again.

It appears you slept thru several semesters of basic electricity
(ELC 102 AC Circuits, ELC 103 Applied AC Circuits).