On 11/6/2014 11:45 AM, rickman wrote:
On 11/6/2014 10:04 AM, Jerry Stuckle wrote:
On 11/5/2014 1:29 PM, rickman wrote:
On 11/4/2014 9:42 PM, Jerry Stuckle wrote:
On 11/4/2014 6:29 PM, rickman wrote:
I am working on a project for receiving a very narrow bandwidth signal
at 60 kHz. One of the design goals is to keep the power
consumption to
an absolute minimum. I'm trying to figure out how to run a
pre-amplifier on less than 100 uW. So far I have found nothing. Any
suggestions?
I agree with Jim. We need many more specifics to provide a meaningful
answer. There are a lot of micropower opamps out there now, but the
devil is in the details.
I've only found one detail that is giving me the devil. That is the
bandwidth. The signal is 60 kHz. I can't think of any other issues I
would have with any amp capable of amplifying this signal with a low
power level. What more info do you feel is needed? Can you ask
questions? Better yet, just point me to any amp that will meet my two
stated requirements!
The other posts you made had the info - things like impedance and gain
are important, as is frequency of operation (but we already know that).
A couple of things to consider, however. The higher the impedance, the
more susceptible it will be to ambient noise pickup. You're starting
with a very small signal and may need to add shielding to limit external
noise.
The other problem is you're asking for low impedance output. Low
impedance limits noise pickup, but increases current drain. So how low
of an impedance do you want?
I don't follow on this. How does a low output impedance drive the
current drain?
There are op amps with very high (in the gigaohm range) input impedance
and pretty low quiescent current drain. How much it draws during use
will be greatly dependent on the output current required, which
obviously depends on output voltage and impedance.
Consider the current used only by the amp, not the load.
I don't have time right now, but later today I'll look through some of
my data sheets on op amps to see what I can find.
Thanks.
Total current is not just dependent on output current; it also is
affected by the design of the chip. Op amps are not just single
transistor devices; a lower output impedance also means more current to
drive the output stage, which affects other components. So even if you
have a high impedance load, the lower the output impedance of the op amp
(i.e. the more current it can source/sink at a specific supply voltage),
the more overall current the op amp will draw.
With that said, I did some looking around (sorry for not getting back to
you quicker - yesterday was pretty busy). Depending on your needs,
there are hundreds you can choose from. I might recommend you check out
http://www.mouser.com/Semiconductors...mps/_/N-6j73m/
.. You can pick and choose the parameters you want. Another one I've
used is
http://www.newark.com/operational-amplifiers.
Between the two I found several hundred possibilities, but you know the
details of what you want better than I do, so rather than guess at what
you might want, I think this would be better. It should give you a start.
--
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Jerry, AI0K
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