One thing that is hidden in AC and later CMOS is very tightly controlled
edge-rate to combat ground bounce. The original AC components were so
fast, the ground bounce could be measured in volts and they had to be
quickly redesigned.
For the D-FF function, you might consider using one section of the dual
74LVC74. With the inputs of the unused section connected to ground or
Vdd, it will draw no power.
David N1HAC
On 6/8/15 8:30 PM, Dan Watson wrote:
I have something of a follow up question. How good is the isolation inside
these devices (74LVC, SOT-23 package) between gates?
Let's say I have a 20MHz TCXO. I want to square up the output signal and
divide by two. Easy, just a buffer or inverter and a flip flop. But looking
at the pinout of the 74LVC1G175 (D flip flop) it doesn't have a Q not
output. So now I need a second inverter to make it toggle. The 74LVC2G14
includes two schmitt inverters in the package, but will isolation inside
the device be good enough to use it for two separate functions at 20 and 10
MHz?
Just from a layout perspective using three devices instead of two would be
easier. However the thing will be battery powered, so I'd like to save the
power if possible.
Thanks
Dan
On Mon, Jun 1, 2015 at 6:13 PM, Andy <[email protected]> wrote:
The gates on that page
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html
use bipolar transistors. The 74LVC parts are CMOS. There are various
effects caused by that difference.
And those examples have vastly inferior control over input switching
levels, compared to just about any well made digital IC from the last half
century. (Funny to think that it has been half of a century!)
2N2222 type transistors might have switching delays upwards of 100 ns
(depending on load), whereas the LVC parts switch in the 1-5 ns range.
"On the other hand: A well designed discrete circuit can beat a general
purpose integrated circuit in almost all performance measures."
Some performance metrics would be hard to beat with even a well designed
discrete circuit. On-die capacitance and inductance tends to be much
smaller than any discrete circuit can achieve.
Andy
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
