[sdiy] CMOS chip questions

[Dan Snazelle]

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

thanks




----------------------------------------
> From: gsn10 at hotmail.com
> To: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] CMOS chip questions
> Date: Sat, 18 Jul 2009 10:47:39 -0400
>
>
> Use 40xx.
>
> ----------------------------------------
>> From: subjectivity at hotmail.com
>> To: usenet at teply.info; synth-diy at dropmix.xs4all.nl
>> Subject: RE: [sdiy] CMOS chip questions
>> Date: Sat, 18 Jul 2009 14:00:38 +0000
>> CC:
>>
>>
>> what about if you need higher supply? (+12volts) is there any replacement for 74C??
>>
>> thanks
>>
>>
>>
>>
>> ----------------------------------------
>>> From: usenet at teply.info
>>> To: synth-diy at dropmix.xs4all.nl
>>> Subject: Re: [sdiy] CMOS chip questions
>>> Date: Sat, 18 Jul 2009 14:49:17 +0200
>>>
>>> Am Saturday 18 July 2009 01:48:01 schrieb Scott Nordlund:
>>>> 74HC is usually fine. I prefer 74HCT since its inputs are TTL compatible.
>>>> If you need something faster, use 74AC. The problem with diode logic (I
>>>> guess you're using diode resistor logic?) is that you can't really chain
>>>> stuff together. The speed depends on your choice of diodes and resistors
>>>> as well as whatever you're driving. I believe TTL circuits prefer pull-up
>>>> resistors rather than pull-down (doesn't matter with CMOS), so this may
>>>> limit your options in some cases.
>>>>
>>> I'll agree totally here, 74HC instead of CD4xxx is usually just fine unless
>>> you really need the devices to withstand 15V Logic levels. And in the 74HC4xxx
>>> series you'll get the very same pinout as the original CD4xxx devices, so
>>> that is a non-issue as well. With most small-scale suppliers, 74HC has better
>>> availability than CD4xxx anyways. When it comes to single gates, there are
>>> such on the market as well. Okay, all i've seen are SMT devices, but when you
>>> need to save real estate, i'd go for that anyways. It ain't no black magic. A
>>> bit pricey in terms of $$/gate compared to the usual 4-gates-in-a-case stuff,
>>> but a lot easier to work with considering all those design questions popping
>>> up when working with discrete Diode-resistor logic. And: if you should happen
>>> to not use some gate in a case, you'll most likely be better of with spending
>>> a couple resistors and tieing those inputs to high or low.
>>> Regarding 74HC vs. 74AHC vs. 74AC in most cases you're safe going for 74HC.
>>> Coz, when you actually need the additional speed of 74AC and AHC compared to
>>> plain 74HC, you'll know anyways. In all those cases with SDIY i've ever come
>>> across, 74HC had plenty of speed and still loads of margin. It's not like
>>> clock jitters of half a nanosecond would kill us here.
>>>
>>> HTH,
>>> Florian
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
> _________________________________________________________________
> Bing™ brings you maps, menus, and reviews organized in one place. Try it now.
> http://www.bing.com/search?q=restaurants&form=MLOGEN&publ=WLHMTAG&crea=TXT_MLOGEN_Local_Local_Restaurants_1x1
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy