fet op amps, max differential input

Dec 28, 2007 4 Replies

Looking at datasheets for op amps that can take a large differential input. TLC271 says +/-Vdd TL071 says +/- 30volts does this mean Tl071 input can go beyond the rail but TLC271 can't?


Dunno. Why don't you post the relevant parts of both data sheets instead of asking us to do your legwork?

OK -- here's the story. Absolute maximum ratings are like Yul Brynner in "The Ten Commandments" saying, "Exceed these and you shall surely die". Very important, which is why they usually put 'em first, but not exactly what you want. You're looking for the working electrical characteristics, which are usually below in the fine print.

You want to look at the input common mode voltage range, listed inside the data sheet.

The TL071 definitely isn't what you're looking for -- it lists V(ICR) (min) as +/-11V for a +/-15V supply, meaning that to be absolutely sure, you can't let the input signal get within 4V of the power supply rails.

The TLC271 is a bit of an odd beast, because it has a bias select pin which basically makes it three different user-selectable op amps (with three similar data sheets). But looking at all three (high, meduim and low bias), the input characteristic in question is the same. At

25C, you can actually go 0.2V below the negative rail, and must stay within 0.8V of the positive rail. For any and all conditions, you have to stay within 1.5V of the positive rail.

You may have experienced a little irritation from other posts about your question. You've more than likely got the data sheets in front of you in another window or tab. Why not copy & paste a link, like this?

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Cheers Chris

link/tlc271.pdf

Yeah, I was in a hurry to click send and get out the door. Thanks for the response.

gearhead schrieb:

Ok, then

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when the stress is gone...

- Udo

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