[sdiy] 1N914 vs. 1N4148 ?

[KA4HJH]

>The 0.5% comes in applications that are above the rating of one diode
>and below the other.  I don't have the data sheets in front of me... but
>I believe there
>is a difference in PIV (peak inverse voltage) and also current rating.
>
>Now (imho) only a jack at ss would use either of these as 'power
>rectifiers'...
>and / or use them where they expected high voltgaes.  In +/-15V
>supplies, in
>most reasonably designed circuits, they are pretty much interchangable.
>
>I have never seen a circuit where one WOULD work and the other would
>not...
>So I can't give a better example...
>
>H^) harry

I made a point of looking it up once. IIRC, the PIV of the 1N914 is 75V and
the 1N4148 is 50V. The 1N4148 is the faster of the two but this won't make
any difference in an audio circuit. Both are *much* faster than
1N400x/1N500x rectifiers, which are too slow/leaky for some critical audio
applications.

In power supply design there is a famous rule of thumb--always use a
rectifier that's rated at least twice the peak unfiltered voltage. This is
because in a traditional power supply a rectifier is reverse-biased with -V
from the transformer on one side and (approximately) +V from the filter
capacitor at the bottom of one half of the cycle. This gives a maximum
potential of ~2V across the rectifier. I'm sure more than one newbie has
been caught by that one. With a 24V RMS transformer the peak potential will
be over 65V so a 50V rectifier will be toast even though "it's only a 24V
power supply".

In the type of audio circuits we're talking about here the the potential is
never going to be higher than the voltage across the rails. I wouldn't
worry about it in this context.

-- 

Terry Bowman, KA4HJH
"The Mac Doctor"