You can build a negative impedance converter easily enough in Spice:
X
A 0----+ +-----0-----+
| F1 = I(E1) | |
/ \ / \ |
/ | \ / + \ ----- |C| = -C
\ V / \ - / -----
\ / E1 = \ / |
| VA - VB | |
B 0----+ +-----0-----+
Y
.subckt negcap A B
F1 A B E1 1.0
E1 X Y A B 1.0
C1 X Y <positive-value>
.ends negcap
If your Spice doesn't allow the current in E sources to control
other sources, then you need to insert a zero-valued V source in
series with the E source to measure the current.
--Eric
>>>>> "Rajkumar" == Rajkumar <[email protected]> writes:
Rajkumar> Hi all,
Rajkumar> I am using some Opamps in a A/D test board. I wan to do
Rajkumar> some simulations on the reference circuit. I am taking
Rajkumar> the Opamp model from the Opamp manufactures. My problem
Rajkumar> is The spice model contains One Negative capacitor which
Rajkumar> denotes that there is a Zero in the Right Half
Rajkumar> Plane. But the simulation doesn't run with this Negative
Rajkumar> capacitance value. So, we have to comment out the line
Rajkumar> and run it which may not give right results. Is there
Rajkumar> any workaround for this problem.
Rajkumar> Looking forward for your mails.
-- J. Eric Bracken, Ph.D. Tel: 1.412.261.3200 x135 Group Leader, Signal Integrity R&D Fax: 1.412.471.9427 Ansoft Corp., Four Station Square, Suite 200 [email protected] Pittsburgh, PA USA 15219-1119 http://www.ansoft.com**** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****