The forward voltage drop is another diode characteristic to be considered for a voltage clamp. These measurements were made as follows (the data is presented graphically in ):
1. Forward bias the diode with a quiet DC supply that has fine resolution; in this case an EDC calibrator
2. With function generator set to pulse, 1 Hz, 1% duty cycle, drive a mercury wetted reed relay. Connect the relay contacts across DUT such that the DUT is shorted for 990 msec and unshorted for 10 msec; this is to minimize self heating effects.
3. Measure forward voltage with Tektronix MSO4104 scope with Model 100 Series' probes to minimize the low forward current errors. Set the scope’s bandwidth limit to 20 MHz to minimize noise. Use the scope’s vertical channel’s offset mode and 10 mV range, adjusting the offset knob until trace is in center of screen, then document the offset voltage.
In conclusion, some simple measurements can provide much insight into the components that you think might be ideal in a given application; and they might reveal some things that are unexpected.