[sdiy] CMOS chip questions

[Dan Snazelle]

hey by the way.,...when interfacing CMOS and TTL, i often see the 4008 mentioned...is this the best way to go?

i wasnt aware until recently that TTL and CMOS had different turn on and turn off voltage requirements so i am looking for ways to 
make them work together

thanks









----------------------------------------
> CC: subjectivity at hotmail.com; gsn10 at hotmail.com; synth-diy at dropmix.xs4all.nl
> From: tom at electricdruid.net
> Subject: Re: [sdiy] CMOS chip questions
> Date: Sun, 19 Jul 2009 14:14:38 +0100
> To: dixon at interchange.ubc.ca
>
>
> On 18 Jul 2009, at 16:43, David G. Dixon wrote:
>
>>> well i meant in a situation where you are trying to replace 74 TTL
>>> with a
>>> higher voltage CMOS compatible TTL.
>>>
>>> i suppose i should just learn to design with actual 5 volt 74LS
>>
>> I think the most convenient way to go when mixing digital and
>> analog is
>> simply to add a 5V supply to the board for digital IC's with
>> 78L05. Then
>> you can use whatever digital IC's are best for a given application,
>> and you
>> don't need a stand-alone 5V supply.
>>
>> Of course, the gurus may beg to differ. I'd be interested in
>> hearing the
>> arguments against this notion.
>
> I'm not claiming "Guru" status just yet either, but that's what I'd
> do. If you've got a lot of logic or digital stuff, then add a +5V to
> your power supply. Otherwise, just stick a regulator on the board
> that needs it. It works fine.
> I suppose you could make a case that individual +5V regulators on
> each circuit board (rather than one global +5V supply) might help
> isolate any digital noise (since digital supplies are not shared).
> Still, I've done it both ways in the past and not seen much difference.
>
> For what it's worth, Bruce Duncan uses individual +5V regulators with
> his digital Modcan modules. He might qualify for "Guru" status!
> (Care to chip in, Bruce?)
>
> HTH,
> Tom
>
> (Just come back from SDIY UK in Cambridge)
>