🚀 go-pugleaf

Mike McCarty wrote:

> In article <8alm5q$g85$1@copland.udel.edu>,
> Ron Dozier <dozier@copland.udel.edu> wrote:
> )In article <89smse$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.
>
> This is good.
>
> )
> )An operational amplifier on the other hand is a general purpose building
> )block and is single ended.
>
> This is wrong.
>
> )A typical use for an IA is thermocouple signal conditioning or bridge
> )amplifier and data acquisition where ground loops are a problem.
> )>
> )
> )Ron
> )
>
> The difference between an op-amp and an instrumentation amp is quite
> simple: an instrumentation amp is an optimized op-amp. It is normally
> built out of more than one op amp. It provides
>
>         low leakage
>         low offset
>         low drift (with temperature and time)
>         high common-mode rejection
>
> That's about it.

Now that is not exactly correct...
    An ideal instrumentation amp generally is a differential input amplifier that
provides fixed stable gain..  i.e. v_out=[(v_in_A)-(v_in_B)]*K
where K is usually fixed and _comparitively_ low ( say 1000 maximum)

An ideal Op Amp looks almost like that _but_ K is very high.

Also the corner frequency for an Op Amp is quite a bit lower (about 100 to perhaps
1000 Hz) than that of an instrumentation amp (hopefully greater than 1KHz to
perhaps as high as 100KHz or more).  Both devices have _roughly_ similar gain
bandwidths.

>
> --
> ----
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