If all you want to do is, say, pick resistors to get the right gain and such, you don't need an opamp model in Spice. An 'e' thing works just like an opamp but doesn't need power supplies. This one does what I want to do, using only resistor values already on my board. It's a nuisance to find a combination that works, but Spice sure beats doing this with a calculator. I find myself Spicing really dumb passive circuits, because it's easier than doing the math manually.
Version 4 SHEET 1 1116 680 WIRE 352 48 256 48 WIRE 416 48 352 48 WIRE 256 96 256 48 WIRE -16 112 -80 112 WIRE 112 112 64 112 WIRE 208 112 112 112 WIRE -80 128 -80 112 WIRE 416 128 416 48 WIRE 208 160 160 160 WIRE -80 240 -80 208 WIRE 256 240 256 176 WIRE -16 320 -80 320 WIRE 112 320 112 112 WIRE 112 320 64 320 WIRE 160 320 160 160 WIRE 320 320 160 320 WIRE 416 320 416 208 WIRE 416 320 320 320 WIRE -80 336 -80 320 WIRE 416 352 416 320 WIRE -80 448 -80 416 WIRE 416 480 416 432 FLAG 256 240 0 FLAG -80 240 0 FLAG -80 448 0 FLAG 416 480 0 FLAG 352 48 OUT FLAG 320 320 FB SYMBOL e 256 80 R0 WINDOW 0 55 42 Left 2 WINDOW 3 48 76 Left 2 SYMATTR InstName E1 SYMATTR Value 100K SYMBOL voltage -80 112 R0 WINDOW 0 -115 38 Left 2 WINDOW 3 -111 80 Left 2 SYMATTR InstName Vref SYMATTR Value 3.00 SYMBOL res 432 224 R180 WINDOW 0 -77 73 Left 2 WINDOW 3 -92 36 Left 2 SYMATTR InstName R1 SYMATTR Value 36.5K SYMBOL res 80 304 R90 WINDOW 0 74 54 VBottom 2 WINDOW 3 80 49 VTop 2 SYMATTR InstName R2 SYMATTR Value 24.9K SYMBOL res 432 448 R180 WINDOW 0 -81 81 Left 2 WINDOW 3 -102 43 Left 2 SYMATTR InstName R3 SYMATTR Value 6.49K SYMBOL voltage -80 320 R0 WINDOW 0 -133 46 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 WINDOW 3 -200 101 Left 2 SYMATTR InstName Vdac SYMATTR Value PULSE(0 3 1 2) SYMBOL res 80 96 R90 WINDOW 0 -43 55 VBottom 2 WINDOW 3 -36 53 VTop 2 SYMATTR InstName R4 SYMATTR Value 1.33K TEXT 736 376 Left 2 !.tran 4 TEXT 512 88 Left 2 ;OPAMP REG FOR DAC-TRIMMED +20 SUPPLY TEXT 672 256 Left 2 ;JL Jan 27, 2017 TEXT 696 320 Left 2 ;19.36 +-0.5 V