On Mon, 23 Sep 2019 at 02:36, johncharlesgord via Groups.Io <johngord=
[email protected]> wrote:
Dave,
50 ohms to ground provides some protection, but often not enough.
The standard human body model (HBM) for ESD testing is 1500 ohms in
series with 100pF. The 1500 ohms is supposed to represent the impedance of
the discharge path through the body, while the 100pF represents the
capacitance of the body including something like rubber soled shoes to a
grounded surface.
Even at a relatively low static voltage like 1500v, one ampere can
(briefly) flow, causing a drop of 50 volts across the 50 ohm resistor.
Small geometry semiconductors like those used in RF mixers can be damaged
by such a hit. Some situations can generate static voltages that are much
higher.
--John Gord
Thank you. I was unaware of that. Perhaps that¡¯s why my 8720 says no ESD on
the front panel. However, the test ports on that are no 50 ohns at DC, as
there are bias-T fitted too.
I assume that there must be some minimum amount of energy required to
damage a semiconductor.
Dave.
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
Telephone 01621-680100./ +44 1621 680100
Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom
