11 Feb
2014
11 Feb
'14
7:15 p.m.
From: Paul Koning: Tuesday, February 11, 2014 9:35 AM
Yes, the D664 is used in much the same way today's designer would
use a Schottky diode. Presumably because Schottky diodes were not
in common use at the time.
On Feb 11, 2014, at 12:17 PM, David Riley
<fraveydank at gmail.com> wrote:
> On Feb 11, 2014, at 9:49 AM, Vincent Slyngstad <vrs at msn.com> wrote:
>
> ...
>> The D664, however, wants the forward drop as low as possible.
If you're
looking for low forward voltage drops, you could also try a
Schottky diode, which also tend to be fairly fast. Some may be hard
to find in through-hole, but depending on how worried you are about
visual authenticity, you could wire up some surface-mount packages
either with actual wires or with a tiny PCB jig.
I?m a bit puzzled by this ?low voltage drop? requirement. Yes, Schottky
will do that, though I didn?t think those were in common use back then. From what I remember of long ago physics and EE, the
forward drop
of a junction diode is a function of the material and does not change
significantly from device to device. So if you?re looking at a silicon
junction diode (as the 1N914 is), the forward drop should be pretty
much the same for all of them.
From a given manufacturer with a given manufacturing
process/plant,
yes. But it isn't considered an important property of a
switching diode.
A different manufacturer, or even a different factory of the same one,
the diode's internal geometry may be different. Some Fairchild 1N914,
for instance, look like 1N4448, and some look like 1N4148. I suspect
they run both processes, and just sell whichever as the 1N914.
Presumably, if you cared (these days), you'd have specified a Schottky
diode. I haven't decided what to think about blanket substitution of
Schottky diodes in the vintage circuits, though.
Vince