NNTP-Posting-Date: Sun, 22 Dec 2002 08:14:36 -0600
From: firstname.lastname@example.org (John Fields)
Subject: Re: how to reduce noise from 555 timer...???
Date: Sun, 22 Dec 2002 14:08:00 GMT
Organization: Austin Instruments, Inc.
References: <3E047B0F.email@example.com> <firstname.lastname@example.org>
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On 22 Dec 2002 04:55:16 -0800, Winfield Hill
>John Fields wrote...
>> There is _no_ reason why the 555 shouldn't operate satisfactorily
>> in this application, especially with all the CMOS 555's available
> The term 555 is generic only if you're referring to one of
> the classic bipolar designs, which have several "flaws" or
> pathologies. Whenever one is referring to one of the CMOS
> variants, some indication should be given, such as CMOS 555,
> or 7555, etc. to avoid confusion. The CMOS and bipolar parts
> aren't interchangable. For example, the easy 50% duty-cycle
> trick that all CMOS 555s can do well, doesn't work at all
> with the bipolar designs. So a simple reference to 555 in
> that context would be misleading and wrong.
Geez, I thought _I_ was the only pedantic old fart around here!
I believe, in the context of the thread, the meaning of my post was
abundantly clear whether or not you choose to "approve" the way I
string words together.
> If the OP was indeed using a bipolar 555 (he would likely
> have said otherwise if not), its supply-crowbar pathology
> coupled with a lack of separate supply filtering and poor
> ground-path wiring, could degrade analog-circuit operation.
Yes, of course, and probably one or more of those is the reason for
his problem. However, there is still _no_ reason why a bipolar 555
shouldn't work satisfactorily if it's properly applied. You may
have noticed that I asked the OP for a schematic, the reason being
that there may be something other than a 555 problem going on, don't
Professional circuit designer