Barrier voltage of diodes Silicium/Germanium: how to measure it and why it is important

Video about the barrier voltage of diodes (Silicium and Germanium) and why this is important. Everything is told in the video, so no more remarks here. To get a precise barrier voltage in some electronic applications you can switch Silicon and Germanium diodes in series. Or, at first, do precise measurements of certain silicon diodes and switch them in series. Say diode A = 0.47 V and diode B = 0.77 V, in series they are 0.47 V + 0.77 V = 0.91 Volt. But you can also use a voltage divider/potentiometer parallel to that bunch of series diodes to align everything to 1/10 of a volt.

The diode that I wanted to show (but had to skip on some moment in the video, at 8.51 in the video) was the RL439 (from a computer board of the 1970's) made by Siemens Germany. Tested it afterwards: on 10 K I measured (3 of them): 0,46 V and 0,51 V and 0,49 V. On 2K5 (2500 Ohm) I measured: 1.2 volt and 1.00 volt and 1.06 volt.

All diodes suffer of temperature effects, by the way, for absolute stability they must be put into an “oven” that gives them a precise and constant temperature.

On the other hand: for precision voltage applications we nowadays have a big bunch of temperature compensated Chips that can do such a job perfectly.

And you can “forward voltage” a Germanium or Silicon (detection) diode, by giving it a tiny (+) voltage on its anode, this can help in e.g. radio detection of AM signals or otherwise (more in other radio video’s on my YT channel).

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