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Subject: Maximum load capacitance that 4000 family cmos devices can handle.
X-Newsreader: Microsoft Outlook Express 5.50.4920.2300
Date: Wed, 6 Nov 2002 13:12:44 -0500
NNTP-Posting-Date: Wed, 06 Nov 2002 13:11:14 EST
Organization: Bell Sympatico
Hi everyones. Thanks to read
On the net in many .PDF files, and also in
mr. Lancaster's CMOS Cookbook...it is said
that a fanout of 50 gates max is recommended
to prevent slow transitions. Since each inputs of
the 4000 family is typically 5 nanofarad and a
maximum of 50 gates is recommended,i assume then
that 250pF is the maximum allowable capacitance
an output can drive. I want to drive a 1500pF
load (the gate of an n-channel power mosfet). The
circuit would be rather ON or OFF for long periods
of times(minutes!) so transition time seems
What i'm worrying about is the 10mA limit for such
devices,and i don't want to latch up the IC and then
destroy it because of too much load capacitance.
Anyone can tell me if a 1500pF gate-source capacitance
from a power mosfet transistor is too much for a 4000
family device...what are the limits? TIA
Alain (alias:Kilowatt) Montreal Quebec
P.S: Excuse me for some errors or omissions,since
I'm a «pure» French Canadian :-)
If replying also by e-mail,remove"no spam"
(with the quotes) from my adress...thanks!
Come to visit me @: http://kilowatt.camarades.com
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