Re: Buffering low capacitance sensors (<50 pF)
- From: Tim Wescott <tim@xxxxxxxxxxxxxxxx>
- Date: Thu, 30 Mar 2006 08:23:29 -0800
Johan van Hespen wrote:
I need ideas for buffering a low capacitance sensor (<50pF). I'm nowWhat's the sensor output? Voltage? Current? I assume that you have a stringent DC offset requirement -- yes?
using high speed opamps like MAX4102, CLC45 etc. in a non-inverting
configuration. The problem is the input biasing. The feedback loop of
this circuit is low-impedance (<1k) so for good biasing the non
invering input the impedance should be of the same order. I can not do
that because the lower cutoff f goes up.
So I need a high input impedance. I need suggestions for alternative
circuits.
Are there any features of the problem that may be leveraged for better performance?
For example, I had a PIN diode opto sensor circuit that I worked on a long time ago. It was part of a scanning system, so there was a period where it was known to be dark. Had the company not run out of money I was planning on putting in an AC-coupled amplifier, and a DC restore circuit synchronized to the diode's dark time.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Posting from Google? See http://cfaj.freeshell.org/google/
.
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- From: Johan van Hespen
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