LT1010 temperature simulation

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Edward Rawde 21 hours ago

Can anyone explain to me why this circuit works exactly as would be expected at .temp 27 and also .temp 26 but with .temp 25 or lower, well, see for yourself.

LTSpice 26.1.1 with all library updates.

Version 4.1 SHEET 1 5432 2900 WIRE -3424 160 -3424 144 WIRE -3424 272 -3424 240 WIRE -3568 336 -3712 336 WIRE -3840 368 -3840 352 WIRE -3648 416 -3648 400 WIRE -3712 432 -3712 336 WIRE -3680 432 -3712 432 WIRE -3568 448 -3568 336 WIRE -3568 448 -3616 448 WIRE -3536 448 -3568 448 WIRE -3424 448 -3456 448 WIRE -3376 448 -3424 448 WIRE -3344 448 -3376 448 WIRE -3840 464 -3840 448 WIRE -3760 464 -3840 464 WIRE -3680 464 -3760 464 WIRE -3424 480 -3424 448 WIRE -3840 496 -3840 464 WIRE -3760 496 -3760 464 WIRE -3648 512 -3648 480 WIRE -3424 576 -3424 544 WIRE -3840 592 -3840 576 WIRE -3760 592 -3760 560 WIRE -3648 656 -3728 656 WIRE -3408 656 -3568 656 WIRE -3520 720 -3520 704 WIRE -3520 720 -3536 720 WIRE -3504 720 -3520 720 WIRE -3952 736 -3984 736 WIRE -3856 736 -3888 736 WIRE -3728 736 -3728 656 WIRE -3728 736 -3776 736 WIRE -3680 736 -3728 736 WIRE -3584 736 -3616 736 WIRE -3504 736 -3504 720 WIRE -3984 816 -3984 736 WIRE -3664 832 -3664 816 WIRE -3536 832 -3536 720 WIRE -3504 832 -3504 816 WIRE -3728 848 -3728 736 WIRE -3696 848 -3728 848 WIRE -3584 864 -3584 736 WIRE -3584 864 -3632 864 WIRE -3552 864 -3584 864 WIRE -3408 864 -3408 656 WIRE -3408 864 -3488 864 WIRE -3696 880 -3728 880 WIRE -3408 880 -3408 864 WIRE -3664 928 -3664 896 WIRE -3520 928 -3520 896 WIRE -3984 944 -3984 896 WIRE -3728 944 -3728 880 WIRE -3408 960 -3408 944 WIRE -3408 1072 -3408 1040 WIRE -3360 1072 -3408 1072 WIRE -3312 1072 -3360 1072 WIRE -3216 1072 -3232 1072 WIRE -3216 1104 -3216 1072 FLAG -3424 144 +v FLAG -3664 816 +v FLAG -3520 704 +v FLAG -3360 1072 output FLAG -3840 592 0 FLAG -3840 352 +v FLAG -3760 592 0 FLAG -3520 928 0 FLAG -3664 928 0 FLAG -3728 944 half FLAG -3424 272 0 FLAG -3648 400 +v FLAG -3648 512 0 FLAG -3376 448 half FLAG -3424 576 0 FLAG -3216 1104 0 FLAG -3984 944 0 SYMBOL voltage -3424 144 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value 27 SYMBOL res -3872 720 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 10k SYMBOL res -3552 640 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 47k SYMBOL OpAmps\\LT1679 -3664 864 R0 SYMATTR InstName U5D SYMBOL OpAmps\\LT1010 -3520 800 R0 WINDOW 0 24 15 Left 2 WINDOW 3 24 38 Left 2 SYMATTR InstName U5 SYMBOL cap -3424 944 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C16 SYMATTR Value 2200n SYMBOL res -3520 720 R0 WINDOW 3 35 47 Left 2 WINDOW 0 36 22 Left 2 SYMATTR Value 56 SYMATTR InstName R61 SYMBOL res -3424 1056 M180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R60 SYMATTR Value 600 SYMBOL res -3328 1088 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R65 SYMATTR Value 600 SYMBOL res -3824 352 M0 SYMATTR InstName R67 SYMATTR Value 10k SYMBOL res -3824 480 M0 SYMATTR InstName R68 SYMATTR Value 10k SYMBOL cap -3744 560 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C18 SYMATTR Value 10n SYMBOL OpAmps\\LT1679 -3648 448 R0 SYMATTR InstName U6 SYMBOL res -3440 432 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R71 SYMATTR Value 1.2k SYMBOL cap -3440 544 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C15 SYMATTR Value 2200n SYMBOL cap -3616 720 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C17 SYMATTR Value 10p SYMBOL voltage -3984 800 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 0.6 1000) SYMBOL cap -3952 720 M90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 2200n TEXT -3912 112 Left 2 !.tran 0 0.4 0 500n startup TEXT -3912 144 Left 2 !.options plotwinsize=0 numdgt=15 TEXT -3912 176 Left 2 !.temp 27

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Jeroen Belleman 21 hours ago

I wouldn't trust OpAmp models for situations where they are driven deep into saturation.

Jeroen Belleman

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Edward Rawde 20 hours ago

"Jeroen Belleman" snipped-for-privacy@nospam.please wrote in message news:11cqjgq$knqj$ snipped-for-privacy@dont-email.me...

But this does exactly the same thing. .temp 27 is fine but .temp 25 and what the??

Version 4.1 SHEET 1 5432 2900 WIRE -3360 320 -3360 304 WIRE -3360 432 -3360 400 WIRE -3248 432 -3360 432 WIRE -3360 464 -3360 432 WIRE -3248 464 -3248 432 WIRE -3360 576 -3360 544 WIRE -3648 656 -3728 656 WIRE -3408 656 -3568 656 WIRE -3520 720 -3520 704 WIRE -3520 720 -3536 720 WIRE -3504 720 -3520 720 WIRE -3856 736 -3984 736 WIRE -3728 736 -3728 656 WIRE -3728 736 -3776 736 WIRE -3680 736 -3728 736 WIRE -3584 736 -3616 736 WIRE -3504 736 -3504 720 WIRE -3984 816 -3984 736 WIRE -3664 832 -3664 816 WIRE -3536 832 -3536 720 WIRE -3504 832 -3504 816 WIRE -3728 848 -3728 736 WIRE -3696 848 -3728 848 WIRE -3584 864 -3584 736 WIRE -3584 864 -3632 864 WIRE -3552 864 -3584 864 WIRE -3408 864 -3408 656 WIRE -3408 864 -3488 864 WIRE -3696 880 -3728 880 WIRE -3664 928 -3664 896 WIRE -3520 928 -3520 896 WIRE -3984 944 -3984 896 WIRE -3408 944 -3408 864 WIRE -3728 976 -3728 880 WIRE -3408 1072 -3408 1024 WIRE -3360 1072 -3408 1072 WIRE -3312 1072 -3360 1072 WIRE -3216 1072 -3232 1072 WIRE -3216 1104 -3216 1072 FLAG -3360 304 +v FLAG -3664 816 +v FLAG -3520 704 +v FLAG -3360 1072 output FLAG -3248 464 0 FLAG -3216 1104 0 FLAG -3984 944 0 FLAG -3360 576 -v FLAG -3520 928 -v FLAG -3664 928 -v FLAG -3728 976 0 SYMBOL voltage -3360 304 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value 13.5 SYMBOL res -3872 720 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 10k SYMBOL res -3552 640 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 47k SYMBOL OpAmps\\LT1679 -3664 864 R0 SYMATTR InstName U5D SYMBOL OpAmps\\LT1010 -3520 800 R0 WINDOW 0 24 15 Left 2 WINDOW 3 24 38 Left 2 SYMATTR InstName U5 SYMBOL res -3520 720 R0 WINDOW 3 35 47 Left 2 WINDOW 0 36 22 Left 2 SYMATTR Value 56 SYMATTR InstName R61 SYMBOL res -3424 1040 M180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R60 SYMATTR Value 600 SYMBOL res -3328 1088 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R65 SYMATTR Value 600 SYMBOL cap -3616 720 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C17 SYMATTR Value 10p SYMBOL voltage -3984 800 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 0.6 1000) SYMBOL voltage -3360 448 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 13.5 TEXT -3920 432 Left 2 !.tran 0 0.4 0 500n startup TEXT -3920 464 Left 2 !.options plotwinsize=0 numdgt=15 TEXT -3920 496 Left 2 !.temp 27

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Jeroen Belleman 19 hours ago

Hmmm. I'm still running V4.21s and both versions simulate just fine, even with .temp 25 or lower.

In fact, it still works the same with .temp -270. Clearly temperature is ignored in the model of the LT1679 I have. I suppose what I have here can't be of further use then.

Jeroen Belleman

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Edward Rawde 19 hours ago

Interesting. the earliest I have here is 26.0.1 with library 270 days old. That still gets a triangular waveform out at .temp 25

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Edward Rawde 19 hours ago

The earliest I have is 24.1.10 with library a year old. It does the same thing.

.options solver=alt doesn't help either.

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someone 17 minutes ago

Because the LT1010 macromodel is natively built into LTspice, its raw SPICE syntax is encrypted or compiled within the software's monolithic standard library file (LTC.lib). Analog Devices does not distribute the standalone unencrypted .SUBCKT text code for this specific, legacy model on their website.

Most commercial operational amplifier (op-amp) SPICE models do not accurately account for temperature because they are heavily simplified macromodels.

Why Most Op-Amp Models Ignore Temperature

• Macromodeling Abstraction: Rather than modeling the dozens of individual internal transistors, diodes, and resistors at the silicon level, standard vendor op-amp models use behavioral voltage/current sources and linear equations. • Fixed Parameters: Internal parameters like open-loop gain ($A_{OL}$), input offset voltage ($V_{OS}$), input bias current ($I_{B}$), and slew rate are often hardcoded to typical room-temperature values (25°C or 27°C). Changing the global simulator temperature via .temp or .step temp in a tool like LTspice Temperature Management will frequently yield little-to-no change in the op-amp's internal electrical behavior. • Missing Die-Level Physics: True temperature effects (such as thermal drift of $V_{OS}$, bandgap voltage shifts, or changing bias currents) require full transistor-level (transistor-level subcircuits) or specialized electrothermal models, which are rarely provided by manufacturers for general-purpose op-amps.

The best you can do: How to Verify or Work Around It

• Check the Datasheet vs. Simulation: Always overlay manufacturer datasheet graphs (such as $V_{OS}$ or $I_{B}$ vs. free-air temperature $T_{A}$) against a .step temp simulation of the specific part (e.g., Texas Instruments THS4001 SPICE Model Performance) to see if the vendor actually embedded temperature dependence. • Inject Temperature Drift Manually: If your op-amp model is static, you can manually parameterize temperature-sensitive error sources (such as placing a small voltage source in series with an input to mimic temperature-dependent input offset drift, or using .param and behavioral sources).

Now you know.

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