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Purpose of LL101 diode used with ICL7660 in biasing circuit.

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Terminator3

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lna-diode-ll101.png
https://www.farnell.com/datasheets/1513917.pdf
ICL7660 is a negative voltage generator,
LL101 is a small signall schottky diode.
I want to know why LL101 diode is used here...

1. to protect gate of FET from positive voltage?
2. ESD protection of FET gates?
3. something else?
 

betwixt

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The only thing I can think of is to prevent damage to the 7660 when the power is turned off. It is possible, although I wouldn't think likely, that the positive supply could couple throught the FETs to the output of the 7660. Other than that I can't see it ever conducts.

Brian.
 

FvM

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I want to know why LL101 diode is used here...
The question presumes that the diode actually serves a purpose. You should also consider that it might be unnecessary.

ICL7660 has already a substrate diode which becomes forward biased when positive currents are fed to the output node. A schottky diode can be meaningful in cases when the current could cause latch-up. The 10k series resistor will prevent this safely.

Most likely, the author copied the diode from a different application without understanding it's purpose.
 
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