How do you come to this conclusion?Becuase discrete zeners dont have high leakage current...
I have to admit, that (@post#5) I wrongly read "uA" instead of "nA". So they are much better than I expected.Actually i notice that the UDZV8.2B (8V2 Zener) is said in its datasheet page 2 to have a Reverse Leakage current of 500nA at VR=5V and 25degC. However, its datasheet on page 4 states that it has a Reverse Leakage current of <10 picoAmps at VR=5V and temp = 25degC.
Do you know which one is correct?
In which case?(BTW Page 4 and page 2 of their datasheets contradict each other over leakage current)
The leakage current will be smaller, but then they don't protect against negative voltage anymore.Also, do you think the “modified back to back zeners” circuit, (also attached) with a MMBD4148 diode in series with each Zener, will reduce the amount of leakage current whilst having the same “back to back” Zener effect?
It does not state "sub 1nA" @ 7V. With 7V I'd say you are too close to the be abke to predict the current.Thanks the fet gates (and zeners) will have 7V on them.
On page 4 of the UDZVTE zener datasheet, it says that leakage current at 125degc is sub 1 nA.
...Surely you agree, this cannot be possible.?....no semiconductor could have leakage current that low at 125degc?
The drive signal is 7V, and we want to be just above that........the Gate is very sensitive and if we choose 11v, then a little overvoltage spike may still kill the gate.Why an 8V zener when the Mosfet can stand 12V?
...thanks, though an input of an opamp would, as you know, obviously be designed and doped to be low in leakage current...a zener is not likely to be designed for low leakage current.I've tested JFET-input op amps at 300C and seen
input leakage below 1uA, there. 1nA at 125C is not
out of the question for small signal devices.
Thanks, and we would be interested in what the leakage really is at 7V?It does not state "sub 1nA" @ 7V. With 7V I'd say you are too close to the be abke to predict the current.
I guess the drive signal is not always 7V. Instead it has a range from xxx Volts to xx Volts.The drive signal is 7V
Yes. But why don´t you use a 9.1V or 10V zener. Then the knee voltage is far away from the 7V and the expected current is more low and can be better determined.the Gate is very sensitive and if we choose 11v, then a little overvoltage spike may still kill the gate.