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Stupid transients in SPICE

I've seen this before, but forget what causes it. Besides dumbass models, obviously. (IRFZ34N is the same ancient '96 MODPEX model you'll find anywhere.)

Bad:

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V2 is: PULSE(0.6 36 1u 1u 1u 100u 200u)

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See the ~ns spikes? Yeah, that's definitely supposed to be there... (No change from adjusting parameters: TRAP vs. GEAR, TRTOL, CHGTOL, etc.)

Good:

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It only seems to depend on R7 being to the drain. Moving C1 from GND to source has no change. Adding a big cap across R1, no change.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com
Reply to
Tim Williams
Loading thread data ...

Alternate solver on?

Cheers

Phil Hobbs

Reply to
pcdhobbs

I'v seen plenty of 2kV+ spikes on noninductive circuits in spice, but I know more about food spices than spice the simulator.

NT

Reply to
tabbypurr

ToySpice will fool you every time >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

                   Spice is like a sports car...  
     Performance only as good as the person behind the wheel.
Reply to
Jim Thompson

That's one of the few things I have learnt. But seriously, I ain't fooled that easily! 2kV on that 5v line with no coils? Er... no.

Yes I know the models use questionable time saving approaches. But it still saves a lot of time compared to the old way of making a proto & endless tweaking.

Then wondering why they sometimes blow up later when everything appears to be in spec, but that's another story. I was young.

NT

Reply to
tabbypurr

Wot's that?

AFAICT the solver is stock XSPICE. Same result for TRAP or GEAR 2.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com
Reply to
Tim Williams

Ah, never mind. Usually when folks moan about stuff like this, it's LTspice they're on about.

Cheers

Phil Hobbs

Reply to
pcdhobbs

Note the SIG: ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

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| 1962 |

Spice is like a sports car... Performance only as good as the person behind the wheel.

Reply to
Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

You killfile is broken, again.

I'd say buzz off, but I'm patient, you'll pass soon.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com
Reply to
Tim Williams

Amateur >:-}

And rude, to boot.

Typical. ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

formatting link
| 1962 |

Spice is like a sports car... Performance only as good as the person behind the wheel.

Reply to
Jim Thompson

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