* SPICE netlist
V1 N001 0 PWL(0 40 1.2m 10)
V2 N006 0 PULSE(5 0 1n 5n 5n 4u 1ms 2)
R1 N001 N002 .1
MQ1 N003 N005 N002 N002 IRF9640
I1 N003 0 PWL(20u 0 500u 1 800u 1 900u .2)
R2 N007 N010 9.53K
R3 N010 0 475
V3 N008 0 5
R4 N008 N009 10K
D1 0 N003 1N914
D2 N005 N002 BZX84C6V2L
R6 N002 N005 100K
R7 N005 N012 100K
R8 N001 N004 100
R9 N001 N011 1Meg
R10 N011 0 13.3K
C1 N011 0 .1
XU1 N002 N006 N009 N009 0 N010 N011 N007 N001 N004 LT6109-1 ;pnba SenseLo)EN/_RST)OutC2)OutC1)V-)INC1)INC2)OutA)V+)SenseHi
MQ2 N012 N009 0 0 2N7002
.tran 1.4m

* LTspice schematic (.asc)
Version 4
SHEET 1 1648 704
WIRE -536 -352 -824 -352
WIRE -200 -352 -536 -352
WIRE 8 -352 -200 -352
WIRE 72 -352 8 -352
WIRE 200 -352 152 -352
WIRE 264 -352 200 -352
WIRE 376 -352 264 -352
WIRE 536 -352 376 -352
WIRE 696 -352 632 -352
WIRE 824 -352 696 -352
WIRE -824 -336 -824 -352
WIRE 8 -336 8 -352
WIRE 264 -336 264 -352
WIRE 696 -336 696 -352
WIRE 824 -336 824 -352
WIRE 376 -320 376 -352
WIRE -536 -304 -536 -352
WIRE -824 -240 -824 -256
WIRE 8 -240 8 -256
WIRE 696 -240 696 -272
WIRE 824 -240 824 -256
WIRE 264 -224 264 -256
WIRE 376 -224 376 -256
WIRE 376 -224 264 -224
WIRE 552 -224 552 -304
WIRE 552 -224 376 -224
WIRE -200 -192 -200 -352
WIRE -152 -192 -200 -192
WIRE 200 -192 200 -352
WIRE 200 -192 168 -192
WIRE 376 -176 376 -224
WIRE -376 -80 -392 -80
WIRE -152 -80 -296 -80
WIRE 232 -80 168 -80
WIRE 232 -64 232 -80
WIRE -312 32 -376 32
WIRE -200 32 -232 32
WIRE -152 32 -200 32
WIRE 232 32 232 16
WIRE 232 32 168 32
WIRE -376 48 -376 32
WIRE 232 48 232 32
WIRE -376 144 -376 128
WIRE -200 144 -200 32
WIRE -152 144 -200 144
WIRE 184 144 168 144
WIRE 232 144 232 128
WIRE 8 208 8 192
WIRE 376 208 376 -96
WIRE -536 240 -536 -224
WIRE -376 240 -536 240
WIRE 184 240 184 144
WIRE 184 240 -376 240
WIRE -536 256 -536 240
WIRE -376 256 -376 240
WIRE -200 288 -200 144
WIRE 328 288 -200 288
WIRE 376 336 376 304
WIRE -536 352 -536 336
WIRE -376 352 -376 320
FLAG 8 208 0
FLAG -824 -240 0
FLAG -392 -80 0
FLAG 824 -240 0
FLAG -376 144 0
FLAG 696 -240 0
FLAG 232 144 0
FLAG 376 336 0
FLAG -536 352 0
FLAG -376 352 0
SYMBOL voltage -824 -352 R0
SYMATTR InstName V1
SYMATTR Value PWL(0 40 1.2m 10)
SYMBOL voltage -280 -80 R90
SYMATTR InstName V2
SYMATTR Value PULSE(5 0 1n 5n 5n 4u 1ms 2)
SYMBOL res 56 -336 R270
SYMATTR InstName R1
SYMATTR Value .1
SYMBOL pmos 632 -304 M270
SYMATTR InstName Q1
SYMATTR Value IRF9640
SYMBOL current 824 -336 R0
SYMATTR InstName I1
SYMATTR Value PWL(20u 0 500u 1 800u 1 900u .2)
SYMBOL res 216 -80 R0
SYMATTR InstName R2
SYMATTR Value 9.53K
SYMBOL res 216 32 R0
SYMATTR InstName R3
SYMATTR Value 475
SYMBOL voltage -376 32 R0
SYMATTR InstName V3
SYMATTR Value 5
SYMBOL res -328 48 R270
SYMATTR InstName R4
SYMATTR Value 10K
SYMBOL diode 680 -272 M180
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL zener 360 -256 M180
SYMATTR InstName D2
SYMATTR Value BZX84C6V2L
SYMBOL res 248 -352 R0
SYMATTR InstName R6
SYMATTR Value 100K
SYMBOL res 360 -192 R0
SYMATTR InstName R7
SYMATTR Value 100K
SYMBOL res -8 -352 R0
SYMATTR InstName R8
SYMATTR Value 100
SYMBOL res -552 -320 R0
SYMATTR InstName R9
SYMATTR Value 1Meg
SYMBOL res -552 240 R0
SYMATTR InstName R10
SYMATTR Value 13.3K
SYMBOL cap -392 256 R0
SYMATTR InstName C1
SYMATTR Value .1
SYMBOL LT6109-1 8 -16 R0
SYMATTR InstName U1
SYMBOL nmos 328 208 R0
SYMATTR InstName Q2
SYMATTR Value 2N7002