Alt-BEAM Archive
Message #01979
To: Sean Rigter rigter@cafe.net
From: Steven Bolt sbolt@xs4all.nl
Date: Fri, 2 Apr 1999 09:44:24 +0200 (CEST)
Subject: [alt-beam] Better 74HC design WAS opamp SE's, RE:74HC240
On Thu, 1 Apr 1999, Sean Rigter wrote:
[ Miller effect ]
---8<---
> This is common in 74HC04 inverters with adjacent input and
> output pins plugged into popular "breadboards" with relatively high pin
> to pin capacitance
I never use breadboards for micropower designs :)
> and is less of a problem in gates that seperate input and output
> pins ie 74HC240. Good layout and "guarding" the input will
> eliminate this problem and gives up to 20% lower current
> consumption at 5V.
The gain is somewhat less pronounced at the 2V micropower level,
but a good layout certainly doesn't hurt. It also helps to
carefully select the manufacturer - the difference between one
chip's power consumption and another's can be hundreds of %.
> I will test at different supply voltages and I believe there are
> some other tricks to speed the transistion through the linear
> input region for ultra low power applications. I will report back
> with the results.
I look forward to reading about them. Note that 74HC micropower
generally means a Vcc of about 2V.
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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