🚀 go-pugleaf

Ron Dozier wrote:
> 
> In article <89smse$fkl$1@news.cz.js.cn>, peter <asdc@bigfoot.com> wrote:
> >Hi,can anyone tell me what's the general difference between
> >instrumental amplifier and operational amplifier? what kind
> >of application does each amplifier designed for?what kind of behaviors or
> >characters we could expect when using them in application
> 
> I'll tak a stab at this question.  An instrumentation amp geneally
> amplifies the differnece between it's inputs in the presence of a large
> common mode signal. They may have an extremely low bandwith.
> An operational amplifier on the other hand is a general purpose building
> block and is single ended.

It might be worth adding that you can make an IA using standard op-amps.
There are various configurations that work well, including a popular
three-amplifier scheme which you can see if you look at the block 
diagram for (as an example) Burr-Brown's INA114 in-amp.  As Ron 
said, IAs are usually intended to have very good common-mode
rejection and this places severe demands on the op-amps and 
resistor matching when you try to make an IA out of several 
op-amps.  That's why integrated IAs are a very Good Thing.
Their bandwidth is not usually so desperately limited
these days, although you can generally improve the common
mode performance somewhat by decreasing the bandwidth (or,
to be fairer, it's extremely hard to achieve good C-M
rejection over a very wide bandwidth).

Jonathan Bromley