What voltages can you put on FET inputs of unpowered chips?

Jan 09, 2008 1 Replies
M

Hi there - I'm working on designing a circuit that uses a LT1540 (datasheet here:

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. I was just about to call it good when I noticed that the absolute maximum ratings for the IN+ pin is V+ + 0.3V. I had been planning on there being times where the chip is not powered (V+ = 0V) but a voltage ranging from about 5-7.5V would be on the IN+ pin. Am I going to release the magic smoke from this chip?



Thanks!


-Michael


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A

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Not an answer to your question, but back in the '80s I did a similar thing with P-CH JFET input opamps, of the LF356 ilk. In my case, the opamp was wired as a voltage follower to buffer a battery voltage to an ADC, and I didn't want the battery loaded when the main supply was off. The opamp + input was 3V above its positive supply, and I couldn't measure any current.

Regards, Allan

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