* SPICE netlist
D1 0 Vref 1N4735A
Q1 N002 N007 N008 0 2N4401
R3 Vout N007 270
R4 N007 0 560
XQ2 Vin N002 N001 tip102 ;pnba C)B)E
V1 Vin 0 SINE(15 3 1)
R5 Vout N001 .33
Q3 N002 N001 Vout 0 2N4401
R6 Vout 0 {R6}
D2 Vin N003 1N4148
D4 N003 N004 1N4148
Q4 Vref N004 P001 0 2N4403
R1 Vin P001 12
R8 N006 0 9.1k
R9 Vref N006 1
V2 Shutoff 0 5
Q8 N002 N004 P002 0 2N4403
R2 Vin P002 47
Q10 Vin N006 N008 0 2N4401
Q6 N009 P003 0 0 2N4401
Q12 N005 N009 0 0 MPSA14
R10 Vin N009 4.7Meg
R11 P003 Shutoff 10k
R15 N004 N005 1k
R16 N008 0 100
.tran 0 1 0 .1
.SUBCKT tip102 1 2 3
Q1 1 2 4 qmodel
Q2 1 4 3 q1model area=11.2198
D1 3 1 dmodel
R1 2 4 8000
R2 4 3 120
+IS=1e-12 RS=10 N=1 XTI=3
+CJO=0 VJ=0.75 M=0.33 FC=0.5
+IS=2.88485e-13 BF=126.335 NF=1.2 VAF=30
+IKF=0.132527 ISE=6.51929e-12 NE=1.9601 BR=0.100001
+NR=1.5 VAR=300 IKR=0.0843484 ISC=1.01027e-13
+NC=1.92564 RB=2.61873 IRB=0.2 RBM=2.61873
+RE=0.0001 RC=2.60372 XTB=0 XTI=4 EG=1.206
+CJE=1.13087e-10 VJE=0.95 MJE=0.692676 TF=1e-09
+XTF=1 VTF=10 ITF=0.01 CJC=1.56651e-10
+VJC=0.908287 MJC=0.23 XCJC=0.897966 FC=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
+IS=2.88485e-13 BF=126.335 NF=1.2 VAF=30
+IKF=0.132527 ISE=6.51929e-12 NE=1.9601 BR=0.100001
+NR=1.5 VAR=300 IKR=0.0843484 ISC=1.01027e-13
+NC=1.92564 RB=2.61873 IRB=0.2 RBM=2.61873
+RE=0.0001 RC=2.60372 XTB=0 XTI=4 EG=1.206
+CJE=1.13087e-10 VJE=0.95 MJE=0.692676 TF=1e-09
+XTF=1 VTF=10 ITF=0.01 CJC=0
+VJC=0.908287 MJC=0.23 XCJC=0.897966 FC=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
.step param R6 list 6 10 15 20 25 50 100 1k 1meg

* LTspice schematic (.asc)
Version 4
SHEET 1 1104 720
WIRE -472 -344 -552 -344
WIRE -456 -344 -472 -344
WIRE -376 -344 -456 -344
WIRE -248 -344 -376 -344
WIRE 88 -344 -248 -344
WIRE 168 -344 88 -344
WIRE 184 -344 168 -344
WIRE 312 -344 280 -344
WIRE 456 -344 392 -344
WIRE 552 -344 456 -344
WIRE 312 -328 312 -344
WIRE 456 -312 456 -344
WIRE -248 -280 -248 -344
WIRE 552 -280 552 -344
WIRE 232 -264 232 -280
WIRE 264 -264 232 -264
WIRE 392 -264 392 -344
WIRE 392 -264 360 -264
WIRE -376 -216 -376 -280
WIRE 24 -216 -72 -216
WIRE 232 -168 232 -264
WIRE 232 -168 88 -168
WIRE 296 -168 232 -168
WIRE -456 -152 -456 -344
WIRE -312 -152 -376 -152
WIRE -72 -152 -72 -216
WIRE -72 -152 -312 -152
WIRE -376 -120 -376 -152
WIRE -248 -72 -248 -104
WIRE -152 -72 -248 -72
WIRE 168 -72 168 -344
WIRE 168 -72 136 -72
WIRE 296 -72 296 -168
WIRE -376 -24 -376 -40
WIRE -328 -24 -376 -24
WIRE -248 -24 -248 -72
WIRE 72 -24 -40 -24
WIRE 440 -24 360 -24
WIRE 456 -24 456 -232
WIRE 456 -24 440 -24
WIRE 280 24 136 24
WIRE 296 24 280 24
WIRE -248 40 -248 24
WIRE -328 56 -328 -24
WIRE -152 56 -152 8
WIRE -40 56 -40 -24
WIRE -40 56 -152 56
WIRE -456 72 -456 -72
WIRE -392 72 -456 72
WIRE 280 72 280 24
WIRE 440 72 440 -24
WIRE -152 88 -152 56
WIRE -392 104 -392 72
WIRE -536 168 -536 152
WIRE -376 200 -392 200
WIRE -328 200 -328 152
WIRE -328 200 -376 200
WIRE -472 216 -472 -344
WIRE -248 216 -248 40
WIRE -152 216 -152 168
WIRE -152 216 -248 216
WIRE 280 216 280 152
WIRE 280 216 -152 216
WIRE 440 216 440 152
WIRE 440 216 280 216
WIRE -376 296 -376 200
WIRE -248 296 -248 216
WIRE -248 296 -376 296
WIRE -536 312 -536 248
WIRE -488 312 -536 312
WIRE -472 312 -472 296
WIRE -472 312 -488 312
WIRE -488 360 -488 312
WIRE -376 360 -376 296
FLAG -552 -344 Vin
FLAG 552 -344 Vout
FLAG -152 -72 Vref
FLAG -488 360 0
FLAG 552 -200 0
FLAG -376 360 0
FLAG -536 152 Shutoff
SYMBOL zener -264 40 M180
SYMATTR InstName D1
SYMATTR Value 1N4735A
SYMBOL npn 360 -72 M0
SYMATTR InstName Q1
SYMATTR Value 2N4401
SYMBOL res 440 -328 R0
SYMATTR InstName R3
SYMATTR Value 270
SYMBOL res 424 56 R0
SYMATTR InstName R4
SYMATTR Value 560
SYMBOL npn 184 -280 R270
SYMATTR InstName Q2
SYMATTR Value tip102
SYMATTR Prefix X
SYMBOL voltage -472 200 R0
SYMATTR InstName V1
SYMATTR Value SINE(15 3 1)
SYMBOL res 408 -360 R90
SYMATTR InstName R5
SYMATTR Value .33
SYMBOL npn 264 -328 M90
SYMATTR InstName Q3
SYMATTR Value 2N4401
SYMBOL res 536 -296 R0
SYMATTR InstName R6
SYMATTR Value {R6}
SYMBOL diode -392 -344 R0
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL diode -392 -216 R0
SYMATTR InstName D4
SYMATTR Value 1N4148
SYMBOL pnp -312 -104 M180
SYMATTR InstName Q4
SYMATTR Value 2N4403
SYMBOL res -264 -296 R0
SYMATTR InstName R1
SYMATTR Value 12
SYMBOL res -168 72 R0
SYMATTR InstName R8
SYMATTR Value 9.1k
SYMBOL res -168 -88 R0
SYMATTR InstName R9
SYMATTR Value 1
SYMBOL voltage -536 152 R0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL pnp 24 -168 M180
SYMATTR InstName Q8
SYMATTR Value 2N4403
SYMBOL res 72 -360 R0
SYMATTR InstName R2
SYMATTR Value 47
SYMBOL npn 72 -72 R0
SYMATTR InstName Q10
SYMATTR Value 2N4401
SYMBOL npn -456 104 R0
SYMATTR InstName Q6
SYMATTR Value 2N4401
SYMBOL npn -392 56 R0
SYMATTR InstName Q12
SYMATTR Value MPSA14
SYMBOL res -472 -168 R0
SYMATTR InstName R10
SYMATTR Value 4.7Meg
SYMBOL res -440 136 R90
SYMATTR InstName R11
SYMATTR Value 10k
SYMBOL res -392 -136 R0
SYMATTR InstName R15
SYMATTR Value 1k
SYMBOL res 264 56 R0
SYMATTR InstName R16
SYMATTR Value 100