* SPICE netlist
RL V2s 0 5.55
VIN Vpos 0 6.35
R1f V2s retro 1.5k
R2f retro 0 1.5k
Rs V2s V1s 0.1
R2 V1s N004 1.15K
R3 N004 0 46k
R4 V2s N001 1.15K
R5 Vs N001 46k
Rx1 ref_in Vref 5k
Ry1 0 ref_in 536
Ra1 retro_in retro 115k
Rb1 0 retro_in 845k
R6 N011 ref_out 2k
R7 N011 retro_out 2k
R8 N012 0 2k
R9 Vref-c N012 2k
R10 N003 0 1k
R11 N003 Vs 1k
R12 N005 Vref-c 2k
R13 Vopamp N005 2k
Q2 N009 N009 N007 0 BC558B
Q3 N002 N009 N008 0 BC558B
Q4 N009 retro N015 0 BC548B
Q5 N002 Vref N015 0 BC548B
R1 Vpos N007 1k
R14 Vpos N008 1k
R15 Vpos N014 1k
Q6 N014 N014 0 0 BC548B
Q7 N015 N014 0 0 BC548B
M1 V1s N002 Vpos Vpos irf9540npbf
V2 Vref 0 PULSE(2.5 2.501 0 10n 10n .1m .2m)
Q1 N002 N010 Vpos 0 BC558B
Q8 N010 Vopamp 0 0 BC548B
R17 Vpos N010 100k
C2 V2s N013 {Cvar}
C3 N006 N002 33n
R16 V2s N006 80
C4 Vpos N002 150p
C5 V2s retro 470p
R18 N013 0 0.3
C6 N010 P001 100p
R19 P001 N002 50
XU1 N004 N001 Vpos 0 Vs TLV247xA ;pnba In+)In-)V+)V-)OUT
XU2 ref_in ref_out Vpos 0 ref_out TLV247xA ;pnba In+)In-)V+)V-)OUT
XU3 retro_in retro_out Vpos 0 retro_out TLV247xA ;pnba In+)In-)V+)V-)OUT
XU4 N011 N012 Vpos 0 Vref-c TLV247xA ;pnba In+)In-)V+)V-)OUT
XU5 N003 N005 Vpos 0 Vopamp TLV247xA ;pnba In+)In-)V+)V-)OUT
C1 Vs N001 2n
C7 Vref-c N012 0.01n
.param RE=1k
#MODELO TRANSISTORES CASA
.step param Cvar list 1u 2.2u 15u
.tran 0 100ms 50ms
.step param Rvar list 6.6 4.4 2 0.01
;step param Rvar list 10 6.6 4 0.01

* LTspice schematic (.asc)
Version 4
SHEET 1 4864 1264
WIRE 528 -568 528 -632
WIRE 672 -536 624 -536
WIRE 784 -536 736 -536
WIRE 400 -520 400 -632
WIRE 528 -456 528 -488
WIRE 624 -456 624 -536
WIRE 624 -456 528 -456
WIRE 656 -456 624 -456
WIRE 784 -456 784 -536
WIRE 784 -456 736 -456
WIRE 848 -456 784 -456
WIRE -2144 -440 -2432 -440
WIRE -1872 -440 -2144 -440
WIRE -1648 -440 -1872 -440
WIRE -1328 -440 -1648 -440
WIRE -1264 -440 -1328 -440
WIRE -1200 -440 -1264 -440
WIRE -1168 -440 -1200 -440
WIRE -832 -440 -1072 -440
WIRE -512 -440 -752 -440
WIRE -96 -440 -512 -440
WIRE 16 -440 -96 -440
WIRE 48 -440 16 -440
WIRE -1264 -344 -1264 -440
WIRE -832 -312 -832 -440
WIRE -752 -312 -752 -440
WIRE 704 -312 704 -328
WIRE -832 -296 -832 -312
WIRE -752 -296 -752 -312
WIRE 528 -296 528 -456
WIRE 672 -296 528 -296
WIRE -1872 -280 -1872 -440
WIRE -1648 -280 -1648 -440
WIRE -1152 -280 -1152 -392
WIRE -1152 -280 -1264 -280
WIRE 848 -280 848 -456
WIRE 848 -280 736 -280
WIRE 928 -280 848 -280
WIRE 1584 -280 1328 -280
WIRE 1744 -280 1664 -280
WIRE 1920 -280 1744 -280
WIRE 400 -264 400 -440
WIRE 672 -264 400 -264
WIRE 2128 -264 1984 -264
WIRE 2400 -264 2128 -264
WIRE 2432 -264 2400 -264
WIRE 1920 -248 1888 -248
WIRE 2400 -248 2400 -264
WIRE -1328 -232 -1328 -440
WIRE 704 -232 704 -248
WIRE -1152 -216 -1152 -280
WIRE -960 -216 -1152 -216
WIRE -848 -216 -896 -216
WIRE -512 -216 -512 -440
WIRE -512 -216 -768 -216
WIRE 400 -216 400 -264
WIRE 1744 -184 1744 -280
WIRE 1888 -152 1888 -248
WIRE 2000 -152 1888 -152
WIRE 2128 -152 2128 -264
WIRE 2128 -152 2080 -152
WIRE 1888 -136 1888 -152
WIRE 400 -88 400 -136
WIRE -1872 -72 -1872 -200
WIRE -1648 -72 -1648 -200
WIRE -1200 -72 -1200 -440
WIRE -2432 -24 -2432 -440
WIRE -1760 -24 -1808 -24
WIRE -1712 -24 -1760 -24
WIRE -1328 -24 -1328 -152
WIRE -1328 -24 -1392 -24
WIRE -1296 -24 -1328 -24
WIRE -1264 -24 -1296 -24
WIRE 1744 -24 1744 -104
WIRE 1888 -24 1888 -56
WIRE -1392 -8 -1392 -24
WIRE -1296 8 -1296 -24
WIRE -1152 24 -1152 -216
WIRE -1152 24 -1200 24
WIRE -512 24 -512 -216
WIRE -368 24 -512 24
WIRE -1552 40 -1600 40
WIRE -1456 40 -1552 40
WIRE -1440 40 -1456 40
WIRE -1872 56 -1872 24
WIRE -1760 56 -1760 -24
WIRE -1760 56 -1872 56
WIRE -2144 88 -2144 -440
WIRE -368 88 -368 24
WIRE 16 88 16 -440
WIRE 464 88 320 88
WIRE 672 88 544 88
WIRE 720 88 672 88
WIRE 768 88 720 88
WIRE -512 104 -512 24
WIRE 912 104 832 104
WIRE 928 104 912 104
WIRE 976 104 928 104
WIRE 1152 104 1056 104
WIRE 1296 104 1152 104
WIRE 768 120 736 120
WIRE 1504 120 1360 120
WIRE 1616 120 1504 120
WIRE 1296 136 1248 136
WIRE -1648 152 -1648 24
WIRE -1296 152 -1648 152
WIRE -1152 152 -1152 24
WIRE -1152 152 -1296 152
WIRE 672 168 672 88
WIRE -1872 200 -1872 56
WIRE -1648 200 -1648 152
WIRE -96 200 -96 -440
WIRE 736 200 736 120
WIRE 928 200 928 104
WIRE 928 200 736 200
WIRE -512 232 -512 184
WIRE -368 232 -368 152
WIRE -368 232 -512 232
WIRE 1248 232 1248 136
WIRE 1296 232 1248 232
WIRE 1328 232 1296 232
WIRE 1504 232 1504 120
WIRE 1504 232 1408 232
WIRE -1936 248 -2000 248
WIRE -1488 248 -1584 248
WIRE -512 248 -512 232
WIRE -512 248 -880 248
WIRE 16 248 16 152
WIRE 1248 264 1248 232
WIRE -2144 280 -2144 168
WIRE -2032 280 -2144 280
WIRE -1488 296 -1488 248
WIRE 672 296 672 248
WIRE -1872 328 -1872 296
WIRE -1760 328 -1872 328
WIRE -1648 328 -1648 296
WIRE -1648 328 -1760 328
WIRE 1296 328 1296 232
WIRE 1344 328 1296 328
WIRE 1504 328 1504 232
WIRE 1504 328 1408 328
WIRE -2144 344 -2144 280
WIRE -1760 344 -1760 328
WIRE -512 360 -512 248
WIRE -2080 392 -2096 392
WIRE -2032 392 -2032 280
WIRE -2032 392 -2080 392
WIRE -1824 392 -2032 392
WIRE 464 424 320 424
WIRE 672 424 544 424
WIRE 720 424 672 424
WIRE 768 424 720 424
WIRE 1248 424 1248 344
WIRE 912 440 832 440
WIRE 928 440 912 440
WIRE 976 440 928 440
WIRE 1152 440 1152 104
WIRE 1152 440 1056 440
WIRE 768 456 736 456
WIRE -2432 472 -2432 56
WIRE -2144 472 -2144 440
WIRE -2144 472 -2432 472
WIRE -1760 472 -1760 440
WIRE -1760 472 -2144 472
WIRE -1488 472 -1488 376
WIRE -1488 472 -1760 472
WIRE -1392 472 -1392 88
WIRE -1392 472 -1488 472
WIRE -1088 472 -1392 472
WIRE -512 472 -512 440
WIRE -512 472 -1088 472
WIRE -224 472 -512 472
WIRE -96 472 -96 280
WIRE -96 472 -224 472
WIRE 16 472 16 328
WIRE 16 472 -96 472
WIRE 64 472 16 472
WIRE 672 504 672 424
WIRE 736 536 736 456
WIRE 928 536 928 440
WIRE 928 536 736 536
WIRE 672 632 672 584
FLAG -1088 472 0
FLAG -2432 -440 Vpos
FLAG 928 -280 Vs
FLAG 400 -632 V1s
IOPIN 2048 -224 In
FLAG 528 -632 V2s
IOPIN 2176 -224 In
FLAG 320 88 Vref
IOPIN 1968 496 In
FLAG 320 424 retro
IOPIN 1968 832 In
FLAG 1616 120 Vref-c
FLAG 1888 -24 Vref-c
FLAG 704 -328 Vpos
FLAG 1952 -232 Vpos
FLAG 1328 152 Vpos
FLAG 800 136 Vpos
FLAG 800 472 Vpos
FLAG 704 -232 Vneg
FLAG 1952 -296 Vneg
FLAG 400 -88 Vneg
FLAG 672 296 Vneg
FLAG 1744 -24 Vneg
FLAG 672 632 Vneg
FLAG 1248 424 Vneg
FLAG 1328 88 Vneg
FLAG 800 408 Vneg
FLAG 800 72 Vneg
FLAG -832 -312 V1s
FLAG -752 -312 V2s
FLAG -224 472 Vneg
FLAG 720 88 ref_in
FLAG 720 424 retro_in
FLAG 912 440 retro_out
FLAG 912 104 ref_out
FLAG -1488 248 Vref
FLAG 2432 -264 Vopamp
FLAG -2000 248 retro
FLAG 1328 -280 Vs
FLAG -880 248 retro
FLAG -1552 40 Vopamp
DATAFLAG 1040 -32 ""
DATAFLAG 96 -32 ""
SYMBOL res -112 184 R0
SYMATTR InstName RL
SYMATTR Value 5.55
SYMBOL voltage -2432 -40 R0
SYMATTR InstName VIN
SYMATTR Value 6.35
SYMBOL res -528 88 R0
SYMATTR InstName R1f
SYMATTR Value 1.5k
SYMBOL res -528 344 R0
SYMATTR InstName R2f
SYMATTR Value 1.5k
SYMBOL res -736 -456 R90
SYMATTR InstName Rs
SYMATTR Value 0.1
SYMBOL Res 384 -536 R0
SYMATTR InstName R2
SYMATTR Value 1.15K
SYMBOL Res 384 -232 R0
SYMATTR InstName R3
SYMATTR Value 46k
SYMBOL Res 512 -584 R0
SYMATTR InstName R4
SYMATTR Value 1.15K
SYMBOL Res 752 -472 R90
SYMATTR InstName R5
SYMATTR Value 46k
SYMBOL Res 560 72 R90
SYMATTR InstName Rx1
SYMATTR Value 5k
SYMBOL Res 688 264 R180
SYMATTR InstName Ry1
SYMATTR Value 536
SYMBOL Res 560 408 R90
SYMATTR InstName Ra1
SYMATTR Value 115k
SYMBOL Res 688 600 R180
SYMATTR InstName Rb1
SYMATTR Value 845k
SYMBOL Res 1072 88 R90
SYMATTR InstName R6
SYMATTR Value 2k
SYMBOL Res 1072 424 R90
SYMATTR InstName R7
SYMATTR Value 2k
SYMBOL Res 1232 248 R0
SYMATTR InstName R8
SYMATTR Value 2k
SYMBOL Res 1424 216 R90
SYMATTR InstName R9
SYMATTR Value 2k
SYMBOL Res 1728 -200 R0
SYMATTR InstName R10
SYMATTR Value 1k
SYMBOL Res 1680 -296 R90
SYMATTR InstName R11
SYMATTR Value 1k
SYMBOL Res 1872 -152 R0
SYMATTR InstName R12
SYMATTR Value 2k
SYMBOL Res 2096 -168 R90
SYMATTR InstName R13
SYMATTR Value 2k
SYMBOL pnp -1808 24 R180
SYMATTR InstName Q2
SYMATTR Value BC558B
SYMBOL pnp -1712 24 M180
SYMATTR InstName Q3
SYMATTR Value BC558B
SYMBOL npn -1936 200 R0
SYMATTR InstName Q4
SYMATTR Value BC548B
SYMBOL npn -1584 200 M0
SYMATTR InstName Q5
SYMATTR Value BC548B
SYMBOL res -1888 -296 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res -1664 -296 R0
SYMATTR InstName R14
SYMATTR Value 1k
SYMBOL res -2160 72 R0
SYMATTR InstName R15
SYMATTR Value 1k
SYMBOL npn -2080 344 M0
SYMATTR InstName Q6
SYMATTR Value BC548B
SYMBOL npn -1824 344 R0
SYMATTR InstName Q7
SYMATTR Value BC548B
SYMBOL pmos -1072 -392 M270
SYMATTR InstName M1
SYMATTR Value irf9540npbf
SYMBOL voltage -1488 280 R0
SYMATTR InstName V2
SYMATTR Value PULSE(2.5 2.501 0 10n 10n .1m .2m)
SYMBOL pnp -1264 24 M180
SYMATTR InstName Q1
SYMATTR Value BC558B
SYMBOL npn -1456 -8 R0
SYMATTR InstName Q8
SYMATTR Value BC548B
SYMBOL res -1344 -248 R0
SYMATTR InstName R17
SYMATTR Value 100k
SYMBOL cap 0 88 R0
SYMATTR InstName C2
SYMATTR Value {Cvar}
SYMBOL cap -896 -232 R90
SYMATTR InstName C3
SYMATTR Value 33n
SYMBOL res -752 -232 R90
SYMATTR InstName R16
SYMATTR Value 80
SYMBOL cap -1280 -344 R0
SYMATTR InstName C4
SYMATTR Value 150p
SYMBOL cap -384 88 R0
SYMATTR InstName C5
SYMATTR Value 470p
SYMBOL res 0 232 R0
SYMATTR InstName R18
SYMATTR Value 0.3
SYMBOL cap -1312 8 R0
SYMATTR InstName C6
SYMATTR Value 100p
SYMBOL res -1312 56 R0
SYMATTR InstName R19
SYMATTR Value 50
SYMBOL opamp2 704 -344 R0
SYMATTR InstName U1
SYMATTR Value TLV247xA
SYMBOL opamp2 800 168 M180
SYMATTR InstName U2
SYMATTR Value TLV247xA
SYMBOL opamp2 800 504 M180
SYMATTR InstName U3
SYMATTR Value TLV247xA
SYMBOL opamp2 1328 184 M180
SYMATTR InstName U4
SYMATTR Value TLV247xA
SYMBOL opamp2 1952 -200 M180
SYMATTR InstName U5
SYMATTR Value TLV247xA
SYMBOL cap 736 -552 R90
SYMATTR InstName C1
SYMATTR Value 2n
SYMBOL cap 1408 312 R90
SYMATTR InstName C7
SYMATTR Value 0.01n