On Wed, 3 Sep 2003 10:39:33 -0700, "Bob"
wrote:

Lower voltage rectifiers are easier to make and therefore cheaper. Further,
they have lower forward drop and are faster. No point in using too high a
rating if these other factors are worth considering.

While the 1 kV 1N4007 is definitely a different creature (with some
PIN diode characteristics) compared to the lower voltage 1N4001-1N4006
rectifiers, I very much doubt that they make separate wafers for
1N4001, 1N4002 etc. but instead try to make, say a 500 V rectifier.

My guess is that they just measure the reverse leakage voltage at
various voltages and print a different label, based on these
measurements. Those passing only the 50 V test will be labelled 1N4001
and sold at a slightly lower price and so on.

If there is a huge order for 1N4001 and there is not enough 50 V units
produced, some units tested OK for 100-500 V are labelled 1N4001 to
full fill the large order. Thus, some selected 1N4001 parts may work
even above 100 V.

Paul OH3LWR