Strange TINA output

Hithesh

Genius 3290 points

I rigged up a circuit to test a MOSFET switch idea.

I am using a N channel mosfet (IRF630) as a switch. The input signal is +/-15V square wave.

I added an op amp buffer coz TINA doesn't let me simulate. The Vee of this buffer is ground.

When I simulate, the output is +/-15V even when the gate voltage is 0V.

The op amp output is also +/-15V even though the vee supply is 0V.

Whats wrong!?

over 14 years ago

0 Rick Downs - WEBENCH Design Center over 14 years ago

TI__Expert 5515 points

Hithesh,

First off, you should get the latest version of TINA-TI - this new version doesn't require you to have a TI component on the schematic anymore, so you wouldn't need the op amp and the potential confusion it is causing. Give that a try and then see if things work better for you. If you still have problems, please post the .TSC file so we can try to help.

0 Hithesh over 14 years ago in reply to Rick Downs - WEBENCH Design Center

Genius 3290 points

1781.Mosfet sw.zip

Rick, I downloaded and simulated with TI TINA 9.

I still get the same kind of output.

TSC file is attached.

0 Rick Downs - WEBENCH Design Center over 14 years ago in reply to Hithesh

TI__Expert 5515 points

Not quite sure what it is you're after, but this is what I'm thinking...

The problem may be the body diode from source to drain, which will always let the +15V pass. If you switch source and drain, this will work more like you expect, I think.

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Strange TINA output