Please can someone tell me if they can replicate this (in a default install of LTspice)?
It's a differential amp set to gain of 0.25 (though unity or other shows same effect). It drives the output hard to the supply rail and stays there! If you replace the LT1213 model with the LT1215 (faster slew rate, twice supply current but otherwise very similar IC), you get the expected standard differential amplifier behaviour.
WHY? :) I've looked to see if there's anything in the data sheet to indicate why, and there isn't, they really look like they should both behave very similarly here.
I've looked at LT's site to see if there's a later (or fixed) model but it's the same, and LT1214 is also the same as 1213 with same error.
Copy below, save as LT1213 Test.asc...
Version 4 SHEET 1 880 680 WIRE 192 128 176 128 WIRE 240 160 224 160 WIRE 96 176 -48 176 WIRE 176 176 176 128 WIRE 192 176 176 176 WIRE -112 192 -128 192 WIRE 272 192 272 128 WIRE 272 192 256 192 WIRE -128 208 -128 192 WIRE -48 208 -48 176 WIRE 96 208 32 208 WIRE 192 208 176 208 WIRE 176 224 176 208 WIRE 224 272 224 224 WIRE 256 272 224 272 WIRE 256 288 256 272 WIRE -128 304 -128 288 WIRE -48 304 -48 288 WIRE -48 304 -128 304 WIRE 32 304 32 288 WIRE 32 304 -48 304 WIRE 176 304 32 304 WIRE 224 304 224 272 WIRE 224 304 176 304 FLAG -112 192 12V FLAG 240 160 12V FLAG 256 288 0 SYMBOL voltage 32 192 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 5V SYMBOL voltage -48 192 R0 WINDOW 3 -2 -39 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value PULSE(0 5V 0 0 0 0.49µ 1µ) SYMBOL res 176 144 R270 WINDOW 0 12 82 VTop 0 WINDOW 3 6 56 VBottom 0 SYMATTR InstName R1 SYMATTR Value 7.5K SYMBOL res 80 192 R270 WINDOW 0 12 83 VTop 0 WINDOW 3 8 56 VBottom 0 SYMATTR InstName R2 SYMATTR Value 30K SYMBOL res 80 224 R270 WINDOW 0 12 83 VTop 0 WINDOW 3 9 56 VBottom 0 SYMATTR InstName R3 SYMATTR Value 30K SYMBOL res 160 208 R0 WINDOW 0 17 26 Left 0 WINDOW 3 19 79 Left 0 SYMATTR InstName R4 SYMATTR Value 7.5K SYMBOL voltage -128 192 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 12V SYMBOL Opamps\\\\LT1213 224 128 R0 WINDOW 0 -19 64 Left 0 SYMATTR InstName U1 TEXT -162 130 Left 0 !.tran 1m startup