15V 7400 logic family??
johns at oei.com
Fri Mar 28 01:07:08 CET 1997
At 11:17 PM 3/27/97 GMT, you wrote:
>On Thu, 27 Mar 1997 08:40:37 -0800, you wrote:
>>I'm designing a nice and simple 2 channel sequencer and, of course, I'd
>>like to make it small and easy to build. Naturally I'm drawn to using CMOS
>>digital ICs because 1) they allow supply voltage of 15V and 2) they consume
>>next-to-nothing power under static conditions. So I looked over the CMOS
>>CD4000 family and found the functionality was kind of light compared to the
>>classic TTL 7400 family.
>Perhaps a little lighter with respect to more hardcore computer
>related binary stuff, but there are other devices that are *perfect*
>for analog signal handling, such as analog multiplexors and
>transmission gates. Perhaps you could let us know what kind of
>devices TTL offers that you'd like to emulate in CMOS. Very often, a
>simple combination of basic elements will yield what is desired. And
>as you say, power consumption is next to nothing, so a small increase
>in package count will not seriously affect power supply design.
Ok, the analog portion of the circuit is pretty simple. I'll use a couple
of CD4051's that will select 1 of 8 voltages from 2 rows of 8 pots and the
4051 outputs going to 2 opamps. The TTL-like device I have my eye on is
and would be the core of this sequencer is a 74161 (4 bit cascadable full
synchronous binary counter). I'm pretty sure that with the features I plan
to design into this, I can use this chip with just several other "glue"
chips as the engine that steps the sequencer. I'm really bent on a lean
design. I don't want to have to fashion a fancy substitute using the
CD4000 series just to make a synchronous counter.
After giving it some thought, it will probably be easiest to simply use the
5V 74HC00 family with an onboard lower power 5V regulator. My working pot
voltage would then be 5V (so I won't blow the 4051's) and I'll amplify the
selected pot voltage with the opamps to get it to the final ouput level
that I need.
John Speth (johns at oei.com)
Object Engineering, Inc.
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