* SPICE netlist
V1 N009 0 PULSE(1.8 3.6 0.7 0 0 0.8 1 5)
R1 N006 N009 900
D1 N002 N006 D
V2 N014 0 PULSE(1.8 3.6 0 0 0 1 2 3)
R2 N003 N002 4700
Q1 N001 N007 N010 0 NPN
Q2 N001 N010 N004 0 NPN
Q3 N002 N005 N008 0 NPN
Q4 N002 N008 N004 0 NPN
R3 N007 N002 2700
R4 N010 N007 7200
R5 N004 N010 3000
R6 N005 N001 2700
R7 N008 N005 7200
R8 N004 N008 3000
R9 N003 N001 680
D2 N011 0 D
D3 N004 N011 D
C2 N004 0 0.0001
R10 N003 N004 1000
Q5 0 N017 N001 0 PNP
V3 N003 0 7
R12 N012 N017 4700
R11 N013 N016 4700
R14 N012 N003 4700
Q6 N012 N013 0 0 NPN
D11 N015 N016 D
D12 N014 N015 D
R13 N016 0 4700
.tran 5

* LTspice schematic (.asc)
Version 4
SHEET 1 2016 800
WIRE 1008 -400 -32 -400
WIRE 480 -368 -656 -368
WIRE 928 -368 560 -368
WIRE -704 -336 -1008 -336
WIRE -208 -336 -704 -336
WIRE 560 -336 560 -368
WIRE 560 -336 -208 -336
WIRE 592 -336 560 -336
WIRE -208 -320 -208 -336
WIRE 928 -320 928 -368
WIRE -1008 -288 -1008 -336
WIRE 480 -224 480 -368
WIRE 480 -224 384 -224
WIRE 592 -224 592 -256
WIRE 592 -224 480 -224
WIRE 736 -208 672 -208
WIRE 928 -208 928 -240
WIRE 928 -208 736 -208
WIRE -208 -192 -208 -240
WIRE -208 -192 -448 -192
WIRE -208 -176 -208 -192
WIRE -96 -176 -208 -176
WIRE -32 -176 -32 -400
WIRE -32 -176 -96 -176
WIRE 208 -176 -32 -176
WIRE 320 -176 288 -176
WIRE 592 -176 592 -224
WIRE 736 -176 736 -208
WIRE -816 -160 -864 -160
WIRE -656 -160 -656 -368
WIRE -656 -160 -752 -160
WIRE -656 -144 -656 -160
WIRE -624 -144 -656 -144
WIRE -512 -144 -544 -144
WIRE -208 -144 -208 -176
WIRE 448 -128 384 -128
WIRE 528 -128 448 -128
WIRE 928 -128 928 -208
WIRE -944 -96 -944 -160
WIRE -352 -96 -448 -96
WIRE -272 -96 -352 -96
WIRE 736 -64 736 -112
WIRE 320 0 320 -176
WIRE 336 0 320 0
WIRE 448 0 448 -128
WIRE 448 0 416 0
WIRE 480 0 448 0
WIRE 592 0 592 -80
WIRE 592 0 560 0
WIRE -512 32 -512 -144
WIRE -464 32 -512 32
WIRE -352 32 -352 -96
WIRE -352 32 -384 32
WIRE -320 32 -352 32
WIRE -208 32 -208 -48
WIRE -208 32 -240 32
WIRE -1008 80 -1008 -208
WIRE -944 80 -944 -16
WIRE -208 96 -208 32
WIRE 592 96 592 0
WIRE 592 96 -208 96
WIRE 672 96 672 -208
WIRE 672 96 592 96
WIRE 928 112 928 -64
WIRE -704 128 -704 -336
WIRE -464 128 -704 128
WIRE 208 128 -384 128
WIRE 384 128 208 128
WIRE -96 176 -96 -176
WIRE 576 176 272 176
WIRE 736 192 736 0
WIRE 384 208 384 128
WIRE -656 224 -768 224
WIRE -544 224 -592 224
WIRE -368 224 -480 224
WIRE -240 224 -368 224
WIRE 16 224 -32 224
WIRE 208 224 208 128
WIRE 208 224 96 224
WIRE 272 256 272 176
WIRE 320 256 272 256
WIRE 576 272 576 176
WIRE -768 336 -768 304
WIRE -368 336 -368 304
WIRE -96 336 -96 272
WIRE 384 336 384 304
WIRE -240 400 -240 224
WIRE 576 400 576 352
WIRE 576 400 -240 400
FLAG -944 80 0
FLAG -768 336 0
FLAG 736 192 0
FLAG 928 112 0
FLAG -1008 80 0
FLAG -96 336 0
FLAG 384 336 0
FLAG -368 336 0
SYMBOL voltage -944 -112 R0
SYMATTR InstName V1
SYMATTR Value PULSE(1.8 3.6 0.7 0 0 0.8 1 5)
SYMBOL res -848 -176 R90
SYMATTR InstName R1
SYMATTR Value 900
SYMBOL diode -752 -176 R90
SYMATTR InstName D1
SYMBOL voltage -768 208 R0
SYMATTR InstName V2
SYMATTR Value PULSE(1.8 3.6 0 0 0 1 2 3)
SYMBOL res 576 -352 R0
SYMATTR InstName R2
SYMATTR Value 4700
SYMBOL npn -512 -192 R0
SYMATTR InstName Q1
SYMBOL npn -272 -144 R0
SYMATTR InstName Q2
SYMBOL npn 320 -224 R0
SYMATTR InstName Q3
SYMBOL npn 528 -176 R0
SYMATTR InstName Q4
SYMBOL res -528 -160 R90
SYMATTR InstName R3
SYMATTR Value 2700
SYMBOL res -368 16 R90
SYMATTR InstName R4
SYMATTR Value 7200
SYMBOL res -224 16 R90
SYMATTR InstName R5
SYMATTR Value 3000
SYMBOL res 304 -192 R90
SYMATTR InstName R6
SYMATTR Value 2700
SYMBOL res 432 -16 R90
SYMATTR InstName R7
SYMATTR Value 7200
SYMBOL res 576 -16 R90
SYMATTR InstName R8
SYMATTR Value 3000
SYMBOL res -224 -336 R0
SYMATTR InstName R9
SYMATTR Value 680
SYMBOL diode 720 -64 R0
SYMATTR InstName D2
SYMBOL diode 720 -176 R0
SYMATTR InstName D3
SYMBOL cap 912 -128 R0
SYMATTR InstName C2
SYMATTR Value 0.0001
SYMBOL res 912 -336 R0
SYMATTR InstName R10
SYMATTR Value 1000
SYMBOL pnp -32 272 R180
SYMATTR InstName Q5
SYMBOL voltage -1008 -304 R0
SYMATTR InstName V3
SYMATTR Value 7
SYMBOL res 112 208 R90
SYMATTR InstName R12
SYMATTR Value 4700
SYMBOL res 560 256 R0
SYMATTR InstName R11
SYMATTR Value 4700
SYMBOL res -368 112 R90
SYMATTR InstName R14
SYMATTR Value 4700
SYMBOL npn 320 208 R0
SYMATTR InstName Q6
SYMBOL diode -544 240 R270
SYMATTR InstName D11
SYMBOL diode -656 240 R270
SYMATTR InstName D12
SYMBOL res -384 208 R0
SYMATTR InstName R13
SYMATTR Value 4700