matching diodes

[Martin Czech]

:::	>So, can diodes be matched with a good meter?  I want to build a
:::ring
:::	>modulator..
:::	>I would perhaps *think* that this is possible on either the ohm
:::setting or
:::	>the diode setting
:::	>
:::	>Rob
:::
:::I selected the diodes for a VCA (diode ring VCA of Minikorg) with my meter
:::in "diode" setting. I don't know for sure, but I assume the numbers in the
:::display are nothing else but the milivolts at a certain constant current.
:::(all in the 500 ...600 range). I took a belt of 1N4148s and alligator clips
:::for the measurements. I left the diodes in the belt, and proceeded until I
:::found
:::four that were within 1mV. (got four matched ones out of 20 or 30)
:::It's quite easy - much easier than matching transistors. Most important: Do
:::not
:::change the temperature of the diodes, i.e. don't touch them with your
:::fingers
:::(easy to avoid as long as they are belted).

I guess the current varries in the different Ohm ranges, indeed diode is
the same as 2kOhm range in most meters.  Measuring in one point is good,
measuring in two points is maybe better, ie. use another range.
It is possible that two diodes have similar voltages for one current,
but have considerable error at some other current, e.g. if a higher knee
voltage is combined with lower parasitic resistance.

m.c.