From: Terry Pinnell
Subject: Re: zero-power toggle circuit; was, how to master electronics
Date: Sun, 17 Nov 2002 16:51:46 +0000
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NNTP-Posting-Date: Sun, 17 Nov 2002 16:52:01 +0000 (UTC)
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Winfield Hill wrote:
>> Win, Jonathan: I'm struggling to understand why I can't get it to
>> simulate. I don't have a BSS110, but tried several alternatives
>> for Q2. Can you positively confirm the circuit's OK please?
> It's OK. Were you careful to connect source of the Q2 p-channel
> FET to the + rail and the source of Q1 n-channel FET to ground?
> I dunno, just a stab in the dark as to what you're doing wrong.
> Are you activating the switch for just a short time, 1/4 second?
>> I downloaded the BS110 Fairchild data sheet which says "They can
>> be used, with a minimum of effort, in most applications requiring
>> up to 0.17A DC". I thought we were talking power switches?
> Hey that wimpy part was Wafer's selection. You can try something
> more serious like an IRF9540, or IRF9Z34N. Or maybe an FB-class
> FET, a real man's part in a SOT-227 bolt-it-in 500W package. :)
By bad luck my initial choice of MOSFET wouldn't toggle at all. But
subsequent tests with a variety of types gave surprisingly
inconsistent results. I've shown my test circuit and results at
Given that my simulation of Win's earlier circuit (using a similar
button-pressing section) seemed 'robust', I'm puzzled why these are
relatively erratic. Is it a flaw in my circuit or interpretation? Or
is the circuit itself genuinely sensitive?
Hobbyist, West Sussex, UK