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-----Original Message-----
From: Panama Mike [mailto:panamatex@...]
Sent: 24 maart, 2003 23:59
To: LTspice@...
Subject: Re: [LTspice] New Feature Released & Opamp Modeling
I put up a version of LTspice today with a
new feature. There's a new symbol attribute
called ModelFile. This lets you specify a
file to include as a library file whenever
this symbol is included. However, the symbol
is still edit-able. This let's you enter
parameters to pass to the subcircuit.
There's two example symbols of the use of
these feature included, 1pole.asy and
2pole.asy in the opamp directory. These
are somewhat ideal opamps with allow the
following parameters to be entered to
model a specific opamp:
Avol open loop DC gain.
GBW open loop gain-bandwidth product
Slew slew rate
Ilimit output current limit
rail how close output can get to the rail
Vos input offset voltage
en equiv. input voltage noise
enk equiv. input voltage noise corner freq
in equiv. input current noise
ink equiv. input current noise corner freq
The model draws all current from the voltage
supplies and has a signal internal node.
Output stage emitter followers are set to 100
Ohms, but you can change that if you need a
more ideal opamp.
The 2pole version has two internal nodes and
an additional parameter, phimargin, which
specifies the 2nd pole in terms of the (approx
-imate) phase margin in degrees.
Input bias, input common mode range and PSRR
are not modeled.
Let me know if you find these things useful.
--Mike
Thanks Mike,
The opamp model is just what I needed.
In the unlikely event that you have nothing to do, please think about a few
thinks:
- display of node numbers in the schematic: no need to remember or label if
you want to make an expression using node voltages.
- a quick way to probe voltages across components. Perhaps alt + left mouse
button?
- a way to store multiple analysis commands. If I use .tran and .ac
commands, only the parameters of the last one is saved, the other gets lost
on exit of the program.
Thanks for you great software and support.
Reinier Gerritsen
The Netherlands
