JFET simulation not working

[pgo48]

I can't for the life of me to get JFETS to work in simulation - I have this circuit which is meant to switch between fully on and fully off. It uses a J177, the on resistance of which is listed on the datasheet as 300 ohms. So, when I switch Vgs to 0v i can expect the voltage over the FET to be shared evenly between the FET and the resistor. When the gate is switched to 15v Vgs is now positive, turning off the FET and the whole voltage is over the FET.

The FET never seems to turn on and the whole supply voltage always shows on the multimeter. Why is this?

[pgo48]

....in this simulation - shorting out the signal with a FET - I can see some FETs work (U310, J309) while others don't (J112, BF545A). Is this a problem with the simulation? Or have I missed something that distinguishes these FETs?

[Josh_E]

Hi pgo48,

I am currently looking into this for you and will update here when I obtain more information regarding this issue.

All the best,

[Josh_E · Accepted solution]

Hi pgo48,

Unfortunately the J177 component is a layout only component, so it does not have a simulation model. The default colour code for a layout only component is green.

The reason these components exist is to aid in PCB design. Simulation models are provided by the manufacturer, below is a link to a simulation model for the J177.

http://www.onsemi.com/PowerSolutions/supportDoc.do?type=models&rpn=MMBFJ177L

You download the MMBFJ177LT1G_SP3_Models from the website and use the tutorial below to create the component for it.

https://decibel.ni.com/content/groups/circuit/blog/2011/04/06/component-creation-101

All the best,

[pgo48]

thankyou!

[jfet]

I uploaded my simulation work and what i am expecting. would please help me to do that? with NI multisim 12