* SPICE netlist
XU1 N011 N005 N001 N009 N006 LT1001 ;pnba In+)In-)V+)V-)OUT
XU2 N006 N013 N001 N009 N012 LT1001 ;pnba In+)In-)V+)V-)OUT
XU3 0 N002 N001 N009 N004 LT1001 ;pnba In+)In-)V+)V-)OUT
XU4 N014 N016 N001 N009 N008 LT1001 ;pnba In+)In-)V+)V-)OUT
R1 N011 N017 270
R2 0 N011 2k2
R3 N005 N010 270
R4 N006 N005 2k2
R5 N012 N013 10k
R6 N013 N018 2k
R7 N018 N020 220
C1 N018 0 3n3
V1 N020 0 {DAC} AC 0
R8 N002 N012 94k
C2 N002 0 1n
C3 N004 N002 1n5
C4 N003 N002 2n2
R9 N004 N003 220
R10 N014 N004 1k
Q1 N001 N008 N015 0 BCW60A
Q2 N015 N019 0 0 BCW60A
Q3 N019 N015 N008 0 BC807-40
R11 N019 0 1k
R12 N015 N008 10
R13 N015 N016 1k
M1 N007 N015 0 0 IRFP250N
R14 0 N010 10m
V2 N007 N010 10 AC 0
V3 N017 0 0 AC 1
V4 N001 0 11
V5 0 N009 11
.ac dec 10 1m 10k
;tran 0 30mm 0m 1u
.STEP param DAC 0.01 3.31 0.25

* LTspice schematic (.asc)
Version 4
SHEET 1 2256 1024
WIRE -488 -512 -616 -512
WIRE -488 -432 -488 -512
WIRE 520 -320 264 -320
WIRE -488 -304 -488 -352
WIRE -184 -304 -312 -304
WIRE -88 -304 -120 -304
WIRE 24 -304 -8 -304
WIRE 520 -272 520 -320
WIRE -872 -256 -904 -256
WIRE -744 -256 -792 -256
WIRE 1128 -256 840 -256
WIRE 456 -224 392 -224
WIRE -616 -208 -616 -512
WIRE -616 -208 -824 -208
WIRE -344 -208 -616 -208
WIRE -312 -208 -312 -304
WIRE -184 -208 -312 -208
WIRE 24 -208 24 -304
WIRE 24 -208 -120 -208
WIRE -552 -192 -696 -192
WIRE -1048 -176 -1128 -176
WIRE -904 -176 -904 -256
WIRE -904 -176 -968 -176
WIRE -824 -176 -824 -208
WIRE 264 -176 264 -320
WIRE 344 -176 264 -176
WIRE -904 -160 -904 -176
WIRE -856 -160 -904 -160
WIRE -552 -160 -552 -192
WIRE -344 -160 -344 -208
WIRE -152 -160 -344 -160
WIRE 264 -160 264 -176
WIRE 264 -160 -152 -160
WIRE 840 -160 840 -256
WIRE -744 -144 -744 -256
WIRE -744 -144 -792 -144
WIRE -584 -144 -744 -144
WIRE -152 -144 -152 -160
WIRE 264 -144 168 -144
WIRE -856 -128 -904 -128
WIRE -456 -128 -520 -128
WIRE -424 -128 -456 -128
WIRE -312 -128 -312 -208
WIRE -312 -128 -344 -128
WIRE -184 -128 -312 -128
WIRE 264 -128 264 -144
WIRE -584 -112 -632 -112
WIRE 24 -112 24 -208
WIRE 24 -112 -120 -112
WIRE 72 -112 24 -112
WIRE 232 -112 152 -112
WIRE 1128 -112 1128 -256
WIRE -312 -96 -312 -128
WIRE -184 -96 -216 -96
WIRE 392 -96 392 -224
WIRE 392 -96 296 -96
WIRE 424 -96 392 -96
WIRE 520 -96 520 -176
WIRE 520 -96 504 -96
WIRE 728 -96 520 -96
WIRE -616 -80 -616 -208
WIRE -552 -80 -552 -96
WIRE -552 -80 -616 -80
WIRE 232 -80 200 -80
WIRE 728 -80 728 -96
WIRE 792 -80 728 -80
WIRE -1048 -64 -1096 -64
WIRE -904 -64 -904 -128
WIRE -904 -64 -968 -64
WIRE -216 -64 -216 -96
WIRE 392 -64 392 -96
WIRE -824 -48 -824 -112
WIRE -696 -48 -696 -192
WIRE -696 -48 -824 -48
WIRE -424 -48 -696 -48
WIRE 264 -48 264 -64
WIRE 344 -48 344 -176
WIRE 344 -48 264 -48
WIRE -904 -32 -904 -64
WIRE 840 -32 840 -64
WIRE 840 -32 760 -32
WIRE 984 -32 840 -32
WIRE -632 -16 -632 -112
WIRE -584 -16 -632 -16
WIRE -456 -16 -456 -128
WIRE -456 -16 -504 -16
WIRE -312 -16 -312 -32
WIRE 520 -16 520 -96
WIRE 520 -16 456 -16
WIRE 984 0 984 -32
WIRE -632 16 -632 -16
WIRE 840 16 840 -32
WIRE 200 48 200 -80
WIRE 296 48 200 48
WIRE 520 48 520 -16
WIRE 520 48 376 48
WIRE -424 64 -424 -48
WIRE -248 64 -424 64
WIRE -152 64 -152 -80
WIRE -152 64 -248 64
WIRE 168 64 168 -144
WIRE 168 64 -152 64
WIRE -904 96 -904 48
WIRE -744 112 -792 112
WIRE -632 112 -632 96
WIRE -632 112 -680 112
WIRE 520 112 520 48
WIRE -248 128 -248 64
WIRE -792 144 -792 112
WIRE -632 144 -632 112
WIRE 392 160 392 32
WIRE 456 160 392 160
WIRE 840 176 840 96
WIRE 1128 176 1128 -32
WIRE 1128 176 840 176
WIRE 392 192 392 160
WIRE -248 240 -248 208
WIRE -632 256 -632 224
WIRE 392 288 392 272
WIRE 520 288 520 208
WIRE 696 336 552 336
WIRE -632 368 -632 336
WIRE 696 368 696 336
WIRE -1096 480 -1096 -64
WIRE 552 480 552 336
WIRE 552 480 -1096 480
WIRE 696 480 696 448
WIRE 760 480 760 -32
WIRE 760 480 696 480
WIRE -1128 512 -1128 -176
WIRE 840 512 840 176
WIRE 840 512 -1128 512
FLAG -904 96 0
FLAG -792 144 0
FLAG -632 368 0
FLAG -312 -16 0
FLAG -216 -64 0
FLAG 392 288 0
FLAG 520 288 0
FLAG -488 -304 0
FLAG -248 240 0
FLAG 984 0 0
SYMBOL Opamps\\OP07 -824 -208 R0
SYMATTR InstName U1
SYMBOL Opamps\\OP07 -552 -64 M180
SYMATTR InstName U2
SYMBOL Opamps\\OP07 -152 -176 R0
SYMATTR InstName U3
SYMBOL Opamps\\OP07 264 -32 M180
SYMATTR InstName U4
SYMBOL res -952 -80 R90
SYMATTR InstName R1
SYMATTR Value 270
SYMBOL res -888 64 R180
SYMATTR InstName R2
SYMATTR Value 2k2
SYMBOL res -952 -192 R90
SYMATTR InstName R3
SYMATTR Value 270
SYMBOL res -776 -272 R90
SYMATTR InstName R4
SYMATTR Value 2k2
SYMBOL res -488 -32 R90
SYMATTR InstName R5
SYMATTR Value 10k
SYMBOL res -648 0 R0
SYMATTR InstName R6
SYMATTR Value 2k
SYMBOL res -648 128 R0
SYMATTR InstName R7
SYMATTR Value 220
SYMBOL cap -680 96 R90
SYMATTR InstName C1
SYMATTR Value 3n3
SYMBOL voltage -632 240 R0
SYMATTR InstName V1
SYMATTR Value {DAC}
SYMATTR Value2 AC 0
SYMBOL res -328 -144 R90
SYMATTR InstName R8
SYMATTR Value 94k
SYMBOL cap -328 -96 R0
SYMATTR InstName C2
SYMATTR Value 1n
SYMBOL cap -120 -224 R90
SYMATTR InstName C3
SYMATTR Value 1n5
SYMBOL cap -120 -320 R90
SYMATTR InstName C4
SYMATTR Value 2n2
SYMBOL res 8 -320 R90
SYMATTR InstName R9
SYMATTR Value 220
SYMBOL res 168 -128 R90
SYMATTR InstName R10
SYMATTR Value 1k
SYMBOL npn3 456 -272 R0
SYMATTR InstName Q1
SYMATTR Value BCW60A
SYMBOL npn3 456 112 R0
SYMATTR InstName Q2
SYMATTR Value BCW60A
SYMBOL pnp2 456 32 R180
SYMATTR InstName Q3
SYMATTR Value BC807-40
SYMBOL res 376 176 R0
SYMATTR InstName R11
SYMATTR Value 1k
SYMBOL res 520 -112 R90
SYMATTR InstName R12
SYMATTR Value 10
SYMBOL res 392 32 R90
SYMATTR InstName R13
SYMATTR Value 1k
SYMBOL nmos 792 -160 R0
SYMATTR InstName M1
SYMATTR Value IRFP250N
SYMBOL res 824 0 R0
SYMATTR InstName R14
SYMATTR Value 10m
SYMBOL voltage 1128 -128 R0
SYMATTR InstName V2
SYMATTR Value 10
SYMATTR Value2 AC 0
SYMBOL voltage 696 352 R0
SYMATTR InstName V3
SYMATTR Value 0
SYMATTR Value2 AC 1
SYMBOL voltage -488 -448 R0
SYMATTR InstName V4
SYMATTR Value 11
SYMBOL voltage -248 224 R180
SYMATTR InstName V5
SYMATTR Value 11