LTspice
John Larkin
analysis sweeps, as a function of pot rotation.
I can't find this. Any other way to simulate the function? I really
need the varying resistances, so I can't just use a multiplier.
John
John Popelish
For a resistance value, use a variable name enclosed in
curly braces (to solve the variable before each run), e.g.
{RV}. Then add a parameter step command to the schematic,
e.g. .step param RV 1 10k 1k
using the Edit, Spice directive menus.
To make a potentiometer, define the values the two halves of
the pot (on each side of the wiper) with a position formula
in curly braces), e.g. {1+Rtotal*position} and
{1+Rtotal*(1-position)}.
Then add a parameter to define Rtotal,
.param Rtotal=10k
and a step command for the position,
.step param position 0 1 .1
The extra ohm in the formulas prevents the section
resistance from reaching zero ohms which blows the math up,
and sort of represents the wiper resistance.
If you want to run single position runs, add a position
parameter definition
.param position=.5
and comment out the step position by right clicking on the
command and clicking the comment button.
Later you can comment out the position parameter and
uncomment the position step command, if needed.
Tam/WB2TT
"John Larkin" <jjla...@highNOTlandTHIStechnologyPART.com> wrote in message
news:n9cbg3h2ie7enqpur...@4ax.com...
potentiometer. But, using the latest version, like you, I could not find it.
Tam
Jim Thompson
Posted many moons ago...
http://analog-innovations.com/SED/PotentiometerForSpice.pdf
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
Joel Kolstad
news:n9cbg3h2ie7enqpur...@4ax.com...
Nope! From hearing Mike Engelhardt (the author) answer the question, I'm
pretty sure it's that way on purpose -- he really does prefer two resistors,
with one set to, e.g., {10k*x} and the other set to {10k*(1-x)}. (And then
you use a .param statement to have LTspice step through the various values of
x you're interested in.)
I'm told that someone has posted (presumably on the Yahoo! group) a
potentiometer just bundling up the two resistors into a single package (as
Jim's .pdf demonstrates) in case you want something that looks "nicer."
It's interesting that Mike seems to feel so strongly about pots one way
whereas John Warner of SIMetrix fame seems to like pots so much he added the
ability to use the cursor keys to "turn" the pot and automatically re-run
simulation each time!
---Joel
John Larkin
I don't suppose that Linear Tech puts many pots on their chips.
I'm still toying with a way to delay a signal 0 to 5 ns with one turn
of a pot, without wrecking the bandwidth and eye diagram. Maybe it
can't be reasonably done.
John
John Popelish
> I'm still toying with a way to delay a signal 0 to 5 ns with one turn
> of a pot, without wrecking the bandwidth and eye diagram. Maybe it
> can't be reasonably done.
Does the pot adjust the clock frequency of a delay line?
John Larkin
wrote:
No, that would be easy, but we want picosecond jitter and at least,
say, 50 ps settability.
I have seen LC delay lines that used varicaps instead of fixed caps,
but that's really nasty. Base delay is big, delta-delay is small,
impedance changes with delay, and tc's are rotten. The HP 8133A pulse
generator does that, and it's a design worh studying, for its
performance and sheer monstrosity.
John
Helmut Sennewald
news:13gcqp9...@corp.supernews.com...
> "John Larkin" <jjla...@highNOTlandTHIStechnologyPART.com> wrote in
> message news:n9cbg3h2ie7enqpur...@4ax.com...
>> Does LTspice have a potentiometer component?
>
> Nope! From hearing Mike Engelhardt (the author) answer the question, I'm
> pretty sure it's that way on purpose -- he really does prefer two
> resistors, with one set to, e.g., {10k*x} and the other set to
> {10k*(1-x)}. (And then you use a .param statement to have LTspice step
> through the various values of x you're interested in.)
>
> I'm told that someone has posted (presumably on the Yahoo! group) a
> potentiometer just bundling up the two resistors into a single package (as
> Jim's .pdf demonstrates) in case you want something that looks "nicer."
Hello,
I have posted a few months ago a second type of pot
into the Files section of the Yahoo group.
The first pot has been controlled with a parameter
while the latest example has a voltage controlled input.
Membership is free!
http://tech.groups.yahoo.com/group/LTspice/
Files > Lib > Potentiometer
Best regards,
Helmut
YD
<jjla...@highNOTlandTHIStechnologyPART.com> penned this immortal
opus:
http://tech.groups.yahoo.com/group/LTspice/files/%20Lib/Potentiometer/
- YD.
--
Remove HAT if replying by mail.