10 Jun
2007
10 Jun
'07
10:22 a.m.
Steve Stutman wrote:
A number of three terminal regulators exhibit problems
if capacitances
they see on their input and/or output are wrong.
dwight elvey wrote:
Many regulators could not handle significant back
voltage. The problem
would often occur if the input had a small capacitor relative to the
output and there was a bleader or other load on the input source.
This was common problem with many CMOS circuits.
Another problem was input over voltage. Often if ther was a transformer
without an input filter capacitor, when the power was turned off, the
inductive spike would wipe out the regulator. It seems like negative
rail regulators were most suseptible to this.
Yes, I was aware of these issues, they're covered in the databooks for the
later regulators in the fine print.
Guessing, but perhaps before these issues were commonly realised or their
solutions incorporated, problems showed up more frequently, and they would
show up in earlier systems which were more likely to be using the 309, and so
the 309 unfairly got a bad rap.
BTW: The earliest reference I found for the 309 was Feb 1971 (Nat Semi Linear
Application Note). Mentioned as one of the motivations for it's development or
uses is distributed/on-card regulation, the technique the Altair/S100 bus
would later take up with.