JFET, IC CA3080 simulation problems

[ZG]

Hi!

1) I am simulating the schematic in Multisim 10 using IC CA3080. The transconductance parameter of CA3080E chip should be regulated by current through pin №5. But CA3080E chip from library always works with fixed gain, which is not dependent from pin №5.

Prototyping of the schematic showed that schematic is 100% workable, but in Multisim it works incorrectly because of CA3080E model.
I have created the equivalent scheme from sources and primitives which works as the CA3080 chip, but without input and output resistances and capacities.
(CA3080E_EQUIVALENT.ms10 file)
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2) 2SK117 JFET transistor has BETA parameter which equals 15. It is right - in datasheet for 2SK117 showed that Yforward=15millisimens.
(Millisimens = 1milliamper/1Volt).
But why in JFET parameters transconductance is measured in mA/V2? What does it mean?

(For JFET transistors transconductance=(2*sqrt(Id*Id0))/Ugs0=[sqrt(mA*mA))/V]=[(sqrt(ma^2))/V]=mA/V)), not mA/sqrt(V), not mA/(V^2).

A simple amplifier with 2SK117 works incorrectly with BETA=15, but starts to work fine when I change BETA parameter to 225.
(JFET SIMULATION PROBLEM.ms10 file)

What is the reason of all these problems ? Is it my fault, or is it Multisim problem ? Or maybe bad libraries ?

Thank you!

Oleg.
Student.
Ukraine.

Message Edited by ZG on 12-11-2007 12:15 PM

[lacy]

To make a long story short, there are a few database issues with Multisim. It is not you as far as I can tell. The only thing we can do when we encounter things of this nature is to report it to NI and hopefully very soon we will see some updates to fix these issues.

It appears to me that you have done the right thing in either finding a different model for your component or adjusted it within the database. We as a community thank you for bringing these issues to light as it might save a person a lot of headaches when their circuits don't work due to faulty component models within Multisim.