Does anyone know offhand of a cheap sample-hold circuit that will work on a single 5 V supply, for input voltages in the range of, say, 1 to 4 V? Most of the stuff turned up by googling is for complete ADCs, which I don't need.
-- John
single-supply s-h
Oct 15, 2006
5 Replies
Except I'd move the switch so the first half of the 6482 doesn't come unglued and possibly railed, causing the switch to leak.
...Jim Thompson
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
You could make your own with a dual opamp and cmos switch as shown on page 21 of:
formatting link
I did have one, made with a 4066 and a TLC2274 as an output buffer, and no input buffer because my input is from a source of less than 100 ohm resistance. The problem I have is charge injection, which gave me a
75 mV jump with a 50 nF cap. I tried breadboarding the circuit you cited, in case it might help the injection, but it doesn't seem to. I did try another analog switch, a MAX326, which has only 1 pC of injection and 1 pA of leakage, and it helped a lot, but it's about a $9 chip, so I'd rather not use it. So if there's a cheap pre-made one-supply s-h that would have lower injection, I'd like to use it. Alternatively, do you know any cheap, hi-spec analog switches?-- John
Sample both your signal and it's reference (AKA ground), and feed them into a differential amplifier. If your switches have well matched charge injection figures it'll bring the error way down -- and it'll set you play remote ground games if you have to.
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Posting from Google? See http://cfaj.freeshell.org/google/
"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
Thanks for the suggestion. Sampling a ground reference through the same chip and system showed a much lower disturbance, so what I thought was charge injection is actually something else. Back to the drawing board.
-- John
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required