> ORIGINAL MESSAGE:
>
> On Mon, 7 Jun 2010 21:12:45 -0600, "Jim Garland" <4cx250b@muohio.edu>
> wrote:
>
>>
>>I've looked at some modern commercial amplifier schematics, and I find no
>>consistent approach. Some use resistor shunts only, some use capacitor
>>shunts only. Those that use molded diode blocks don't use any shunts. So
>>I'm
>>interested in knowing the latest thinking on this subject. Thanks!
>
> REPLY:
>
> The consensus seems to be you don't need either resistors or
> capacitors PROVIDED you get matched diodes. In other words, diodes
> from the same production run. Do not mix diodes bought from different
> sources even if they are the same type and same manufacturer. Buy them
> in one lot from one source.
>
> The worst thing you could do is to mix manufacturers.
>
> The safest way to get matched diodes is to order them on
> tape-and-reel. Then you can be sure they were all made together.
>
> 73, Bill W6WRT
I cant argue with that in theory but in practical use where the diodes are
not operating close to any limiting part of the spec any extra detrius is
not needed, capacitors in particular can be problematic. It is better to run
a single .005 across all the diodes of each string and another to ground at
the common output. This provides a bypass path for line spikes that get thru
as well as diode transients.
Of more importance IMO is the method of mounting the high current versions
such as the 1N5408, 6A10, etc. The leads are part of the heat sink, short
leads and sharp bends right at the case are to be avoided. See manufacturers
specs for details, derating, etc.
>From a quick search it appears that the 1N5553 reverse current is 1ua, and
the 1N5408 is 5ua, both at 25*C. Leakage goes up with temperature.
Carl
KM1H
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