Re: High Voltage leaky diode (or any diode like device)



ferdimh@xxxxxx wrote:
Why don't you consider replacing the Zener?
I'd use a TL431 in a cascode configuration:
32K
-----------/\/\--+----+-- out
| |
| |
| |
| |
1K |/ c \
+--/\/\----| NPN / 22M
12V-+ |\ e \
+--/\/\------+ |
470 | |
/-/ |
TL431 A----+
| |
| \
| / 270K
| \
| |
+----+
|
-+-
GND

The low-voltage supply could be varied between 4 and 36V volts.
The main leak is caused by the 22M resistor. and about 100µA at 200V.
If a BF459 is used, its leak would be max. 5µA at 150 °C junction
temperature. So total error is going to be below 3.5 volts. if that
isn't accurate enough, an emitter follower could be used to drive the
divider. But a circuit needing higher accuracy is not a good design
anyway.

The BF459 is obsolete...and 200V/22M=9uA

.