In article ,
dxAce wrote:


wrote:

Thanks for the info and advice Pete. I recently saw a comment that
standard 1N4002 type (60 Hz) diodes are actually good replacements for
the PIN diodes on the front-end band pass switching networks. Have you
heard of this?

It's supposed to be the higher voltage parts in that series, (the 1N4007).

Whatever happened to all those Schottky Diode mods that seemed to be the rage
years ago? Would this be something similar?

Semiconductor-wise, they're pretty much the opposite.

A Schottky diode uses only one type of semiconductor and the junction
is silicon-metal. (The modern version of a cat's wisker detector).
Their feature is that they don't store a cloud of electrons or holes
inside their junction so that they don't have a feature called "reverse
recovery". (Executive summary, they don't look like a short circuit for
a few nanoseconds when the current switches direction). Reverse recovery
causes all sort of problems in switching power supplies, and is also
the cause of RFI from regular old transformer/rectifier power supplies.

A PIN diode uses both P and N type doping in the junction, but in
addition there is a layer of Intrinsic (neutrally doped) silicon
in the middle. This causes a bunch of stored charge to hang around
in the middle of the junction, so that for high frequencies it doesn't
look like a diode anymore. They're used for switches by forward
biasing them to turn them on, or when reverse biased the stored
charge eventually gets swept out of the junction and they look like
an open circuit (or really, a capacitor). As I understand it,
there's a tradeoff between storage time (and switching speed) and
capacitance. The designer would like as much storage time (sets the
low frequency response) and the minimum capacitance.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)