Are there any special considerations with using P-spice op-amp macro
models with LTspice? I'm trying to simulate a circuit that uses a
Burr Brown/TI electrometer op-amp (OPA128 or OPA129) and I'm getting
incorrect results. I downloaded the models from TI's website. The
circuit's been built and thoroughly debugged, so I'm confident in the
design.
When I couldn't get the circuit to operate correctly, I entered a
simple test circuit to verify some of the basic op-amp
characteristics. I found that the input bias current was way to high
(about 12nA instead of 100fA), and the gain-bandwidth of the OPA129
was high by about a factor of 10. I suspect that the models are just
screwed up, but since I'm new to LTspice I'm not completely confident
with my conclusion. Any help would be greatly appreciated.
I get similar problems with the OP27A, although in my case it is the noise that
is reported about 2 orders more than the data sheet and hand calculations
suggest. The bias currents look right. Other vendors opamps seem to behave.
I ran a test circuit on Accusim II (Eldo SPICE-like kernal) and the OP27A gave
sensible answers. I ported the netlist back to LTSPICE and although the AC
analysis ran, the noise analysis gave up . I put the Accusim OP27A model into
LTSPICE library and it gave the same wrong noise on my test circuit.
Brian
--
Brian Howie | Tel: 0131 343 5590
BAE SYSTEMS | Fax: 0131 343 5050
Sensor Systems Division | Email brian.howie@...
Silverknowes | bhowie@...
Edinburgh EH4 4AD | Web site www.baesystems.com
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