AW: Use of Diodes in Filters??

Haible Juergen Juergen.Haible at nbgm.siemens.de
Thu Nov 20 11:05:36 CET 1997



	>So , using multiple diodes makes matching easier, just by the
first law
	>of statistics : "law of the large number" (in case of a large
number of 
	>elements the distribution will "sharpen" arround some mean
value).
	>
	>But the S/N ratio in the example obove is also a good reason to
	>stack diodes, for shure.

I think these are the two main reasons to use several diodes instead of
one.

Funny side note on selecting: EMS reportedly bought large quantities
of very cheap diodes - cheap for the reason that they might be labelled
wrong, i.e. the cathode ring being either on the kathode or anode side.
So this didn't need selection, but still needed polarity checking.

In my youth I bought a hundred of wrong labelled diodes myself (also
very cheap), but at least these had the kathode ring *all* on the anode
side.

But I disgress.

The "bridge rectifier" in the MS-50 filter is simply to replace two
resistors
in a Low pass filter: 2 diodes for each resistor. Not sure about the 
additional 2 diodes, however. Maybe to even out tolerances by the
law of (not so) large numbers.
The diodes in the opamp feedback loop are to limit signals at self
oscillation.

JH.




More information about the Synth-diy mailing list