The purpose of this circuit, which we found in the November 1986 Radio Electronics issue, is to determine the voltage across a zener diode. Several test currents can be selected.
We found this circuit in a technical documentation on the National Semiconductor LM3909. The...
The LEDs act as diodes, so if good they will show the same characteristic curve. Arrangment shown...
This circuit is from an old English publication from 1968. We can implement it with TIP32...