op amp question

[Albre]

What gain-bandwidth do I need for a 90 degree phase shift op amp that
will operate at less than 3000 Hz?

I found a diagram on the internet, but it specifies a 6 Mhz
gain-bandwidth op amp that uses alot of power. Since I hope to use it
in a battery powered and portable environment, I'd like to use the
lower power part. The original designer wasn't after low power as a
design parameter, I'm hoping that the lower power part will work just
as well.

I was able to find a part that has the same noise rating (actually
better), but the main difference is the gain-bandwidth and the supply
current.

Do I really need to use the 6 Mhz (1.5 ma) gain-bandwidth part, or
will the 400 Khz (60 ua) gain bandwidth part work just as well?

TIA

Albre

 

[John Woodgate]

I read in sci.electronics.design that Albre <?@?.?.invalid> wrote (in
<90ql51l7sf748tclov7998p5k5edtph0h4@4ax.com&gt about 'op amp question',
on Mon, 11 Apr 2005:

Do I really need to use the 6 Mhz (1.5 ma) gain-bandwidth part, or
will the 400 Khz (60 ua) gain bandwidth part work just as well?

What do you mean by a '90 degree phase-shift op-amp'? Bear in mind that
the open-loop response of many op-amps is only a few tens of Hz at most,
so you get quite a lot of closed-loop phase-shift at audio frequencies
unless the closed-loop gain is very low.

You probably don't need the 6 MHz part, but without knowing exactly what
you are trying to do, it isn't possible to advise you properly.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Pooh Bear]

Albre wrote:

What gain-bandwidth do I need for a 90 degree phase shift op amp that
will operate at less than 3000 Hz?

You mean you *want* to create a 90 degree phase shift ? Like one of those
all pass filters ?

I found a diagram on the internet, but it specifies a 6 Mhz
gain-bandwidth op amp that uses alot of power. Since I hope to use it
in a battery powered and portable environment, I'd like to use the
lower power part. The original designer wasn't after low power as a
design parameter, I'm hoping that the lower power part will work just
as well.

I was able to find a part that has the same noise rating (actually
better), but the main difference is the gain-bandwidth and the supply
current.

Do I really need to use the 6 Mhz (1.5 ma) gain-bandwidth part, or
will the 400 Khz (60 ua) gain bandwidth part work just as well?

Oh - you consider 1.5mA to be high power - lol !

If it's the configuration I think you mean, the 400kHz GBW part will be
just fine.


Graham