Basic LTSpice question

I'm (very slowly) learning to play with LTSpice.

For temperature simulations do the models generally have a temperature dependent characteristics built in?

I can do a temp simulation with a Si diode and get some sensible output.

With feeding a fixed voltage from a resistor divider into an op amp follower I get no change in the output with temperature.

Am I correct in thinking the LT op amp models and the resistors have no temperature dependent parameters included?

Are temp dependent parameters only included for diodes and transistors?

Version 4 SHEET 1 880 680 WIRE 176 16 -32 16 WIRE -192 32 -384 32 WIRE -32 32 -32 16 WIRE 336 48 112 48 WIRE -192 112 -192 32 WIRE -32 128 -32 112 WIRE 176 144 176 16 WIRE 112 160 112 48 WIRE 144 160 112 160 WIRE 336 176 336 48 WIRE 336 176 208 176 WIRE 400 176 336 176 WIRE 144 192 -64 192 WIRE -240 208 -288 208 WIRE -192 208 -192 192 WIRE -64 208 -64 192 WIRE -64 208 -192 208 WIRE -384 224 -384 32 WIRE -288 240 -288 208 WIRE -192 240 -192 208 WIRE 176 256 176 208 WIRE -384 320 -384 304 WIRE -288 352 -288 304 WIRE -192 352 -192 320 WIRE -192 352 -288 352 WIRE -192 368 -192 352 FLAG 176 256 0 FLAG -32 128 0 FLAG -384 320 0 FLAG 400 176 out FLAG -192 368 0 SYMBOL voltage -384 208 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 WINDOW 3 -37 161 Left 2 SYMATTR Value 2.5 SYMATTR InstName V1 SYMBOL voltage -32 16 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 5 SYMBOL res -208 96 R0 SYMATTR InstName R1 SYMATTR Value 2K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL Opamps\\LT1012 176 112 R0 SYMATTR InstName U1 SYMBOL res -208 224 R0 SYMATTR InstName R2 SYMATTR Value 4K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL diode -304 240 R0 SYMATTR InstName D1 SYMATTR Value 1N914 TEXT -96 440 Left 2 !.temp 0 10 20 30 40 50 TEXT -96 392 Left 2 !.tran 0 1 0 0.01

Reply to
Aussie
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Different resistors (and caps, and inductors) respond to temperature differently. It's not just the magnitude of the change -- some have positive temperature coefficients, some negative, some have responses that are not straight-line with temperature. So if it matters, you'll need to model the temperature response of the components in question yourself.

Hopefully the paper John cites goes into all that.

--
www.wescottdesign.com
Reply to
Tim Wescott

Understood. Thanks Tim.

PS - I hope you enjoy your new job & still find time to do the odd YouTube video.

Reply to
Aussie

Then there's the serious issue that not all components on a PCB are at the same temp. We have junctions that are rather hot, from tough jobs they're doing, and other parts cruising along at ambient temp.

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 Thanks, 
    - Win
Reply to
Winfield Hill

I'm hoping that'll be the case.

In the short term I have a couple of customers yet to take care of -- they weren't keeping me alive, but I'm still on the hook for significant work.

In the longer term, I should be able to get stuff done. The prospect of changing roles has given me a lot of energy that I thought had just gone away with old age -- time will tell if it holds up or if it's just mental meth.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com
Reply to
Tim Wescott

I was going to leave that for the advanced course. But yes. I'm thankful to not have been on projects like this myself, but I've sat NEXT to some poor bastards that spent months carefully calibrating a board over temperature, only to find that when ambient was changing the calibration didn't hold because of uneven temperatures. They cried. I was sympathetic, but inside I was very thankful that It Wasn't Me.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com
Reply to
Tim Wescott

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