* SPICE netlist
XU3 N005 Square +30V 0 Square 2TL081 ;pnba In+)In-)V+)V-)OUT
D7 N006 N005 2D1N4148
D8 N005 N010 2D1N4148
D9 N004 N010 2D1N4148
D10 N006 N004 2D1N4148
C4 N004 0 100nf
XU4 0 N004 N005 +12V N009 N004 NC_01 +12V NE555 ;pnba GND)TRIG)OUT)RST)CV)THRS)DIS)Vcc
C3 N009 0 1nF
R8 +12V N013 33k
R9 N013 0 10k
XU6 N013 N011 +12V 0 N012 2TL081 ;pnba In+)In-)V+)V-)OUT
Q2 N010 N012 N011 0 22N3904
R10 N011 0 1k
R11 +12V N003 2.8k
R12 N003 0 10k
XU7 N003 N001 +12V 0 N002 2TL081 ;pnba In+)In-)V+)V-)OUT
Q22N3906 N006 N002 N001 0 PNP
R13 +12V N001 0.5k
V1 +30V 0 30
V2 +12V 0 12
XU1 N004 N008 +30V 0 Triangle 2TL081 ;pnba In+)In-)V+)V-)OUT
Rt_g1 N008 N007 5.6k
Rt_f Triangle N008 10k
Rt_1 +12V N007 680
Rt_g2 N007 0 620
.tran 0 0.005 0.001 0.002

* LTspice schematic (.asc)
Version 4.1
SHEET 1 1872 1200
WIRE 216 -584 8 -584
WIRE 8 -520 8 -584
WIRE 8 -520 -168 -520
WIRE 40 -520 8 -520
WIRE -168 -504 -168 -520
WIRE 216 -488 216 -504
WIRE 216 -488 -56 -488
WIRE 216 -472 216 -488
WIRE 8 -456 8 -520
WIRE -56 -440 -56 -488
WIRE -24 -440 -56 -440
WIRE 152 -424 40 -424
WIRE -168 -408 -168 -424
WIRE -24 -408 -168 -408
WIRE -168 -392 -168 -408
WIRE -104 -312 -168 -312
WIRE 8 -312 8 -392
WIRE 8 -312 -104 -312
WIRE -440 -296 -440 -344
WIRE -440 -296 -664 -296
WIRE -264 -296 -440 -296
WIRE -104 -296 -104 -312
WIRE 680 -248 504 -248
WIRE -232 -232 -584 -232
WIRE 408 -232 -232 -232
WIRE -936 -216 -936 -280
WIRE -808 -216 -808 -280
WIRE 584 -216 584 -280
WIRE 504 -200 504 -248
WIRE 552 -200 504 -200
WIRE 680 -184 680 -248
WIRE 680 -184 616 -184
WIRE 808 -184 680 -184
WIRE 552 -168 -56 -168
WIRE -520 -152 -552 -152
WIRE -264 -152 -264 -296
WIRE -264 -152 -296 -152
WIRE 584 -120 584 -152
WIRE -936 -104 -936 -136
WIRE -808 -104 -808 -136
WIRE -584 -88 -584 -232
WIRE -520 -88 -584 -88
WIRE 536 -72 520 -72
WIRE 216 -56 216 -376
WIRE 216 -56 72 -56
WIRE 264 -56 216 -56
WIRE 520 -56 520 -72
WIRE -520 -24 -584 -24
WIRE -232 -24 -232 -232
WIRE -232 -24 -296 -24
WIRE 72 8 72 -56
WIRE 264 8 264 -56
WIRE 568 24 520 24
WIRE 664 24 648 24
WIRE 696 24 664 24
WIRE 808 24 776 24
WIRE -664 40 -664 -296
WIRE -520 40 -664 40
WIRE -264 40 -296 40
WIRE 520 40 520 24
WIRE 712 56 712 -8
WIRE 664 72 664 24
WIRE 680 72 664 72
WIRE 808 88 808 24
WIRE 808 88 744 88
WIRE 936 88 808 88
WIRE -584 104 -584 -24
WIRE -56 104 -56 -168
WIRE -56 104 -584 104
WIRE 72 104 72 72
WIRE 72 104 -56 104
WIRE 264 104 264 72
WIRE 408 104 408 -232
WIRE 408 104 264 104
WIRE 440 104 408 104
WIRE 680 104 440 104
WIRE -264 136 -264 40
WIRE 72 136 72 104
WIRE 264 136 264 104
WIRE 520 136 520 120
WIRE 712 136 712 120
WIRE 712 136 520 136
WIRE 440 152 440 104
WIRE 712 152 712 136
WIRE -552 200 -552 -152
WIRE -264 200 -552 200
WIRE -264 216 -264 200
WIRE 440 232 440 216
WIRE 72 280 72 200
WIRE 168 280 72 280
WIRE 264 280 264 200
WIRE 264 280 168 280
WIRE -40 312 -216 312
WIRE 24 312 -40 312
WIRE -216 328 -216 312
WIRE 168 360 168 280
WIRE -40 376 -40 312
WIRE -72 392 -104 392
WIRE 104 408 -8 408
WIRE -216 424 -216 408
WIRE -72 424 -216 424
WIRE -216 440 -216 424
WIRE -104 504 -104 392
WIRE 168 504 168 456
WIRE 168 504 -104 504
WIRE -216 584 -216 520
WIRE -40 584 -40 440
WIRE -40 584 -216 584
WIRE 168 584 -40 584
WIRE 168 600 168 584
FLAG -264 216 0
FLAG -440 -344 +12V
IOPIN -16 384 BiDir
FLAG 584 -120 0
FLAG 584 -280 +30V
IOPIN 1008 448 BiDir
FLAG 168 600 0
FLAG 24 312 +12V
IOPIN 448 1040 BiDir
FLAG 40 -520 +12V
IOPIN 464 208 BiDir
FLAG -104 -296 0
FLAG -808 -280 +12V
IOPIN -384 448 BiDir
FLAG -936 -280 +30V
IOPIN -512 448 BiDir
FLAG -936 -104 0
FLAG -808 -104 0
FLAG 712 152 0
FLAG 712 -8 +30V
IOPIN 1136 720 BiDir
FLAG 808 -184 Square
IOPIN 1232 544 BiDir
FLAG 936 88 Triangle
IOPIN 1360 816 BiDir
FLAG 440 232 0
FLAG 536 -72 +12V
IOPIN 960 656 BiDir
SYMBOL OpAmps\\opamp2 584 -248 R0
SYMATTR InstName U3
SYMATTR Value 2TL081
SYMBOL diode 56 8 R0
SYMATTR InstName D7
SYMATTR Value 2D1N4148
SYMBOL diode 56 136 R0
SYMATTR InstName D8
SYMATTR Value 2D1N4148
SYMBOL diode 248 136 R0
SYMATTR InstName D9
SYMATTR Value 2D1N4148
SYMBOL diode 248 8 R0
SYMATTR InstName D10
SYMATTR Value 2D1N4148
SYMBOL cap 424 152 R0
SYMATTR InstName C4
SYMATTR Value 100nf
SYMBOL Misc\\NE555 -408 -56 R0
SYMATTR InstName U4
SYMBOL cap -280 136 R0
SYMATTR InstName C3
SYMATTR Value 1nF
SYMBOL res -232 312 R0
SYMATTR InstName R8
SYMATTR Value 33k
SYMBOL res -232 424 R0
SYMATTR InstName R9
SYMATTR Value 10k
SYMBOL OpAmps\\opamp2 -40 344 R0
SYMATTR InstName U6
SYMATTR Value 2TL081
SYMBOL npn 104 360 R0
SYMATTR InstName Q2
SYMATTR Value 22N3904
SYMBOL res 152 488 R0
SYMATTR InstName R10
SYMATTR Value 1k
SYMBOL res -184 -520 R0
SYMATTR InstName R11
SYMATTR Value 2.8k
SYMBOL res -184 -408 R0
SYMATTR InstName R12
SYMATTR Value 10k
SYMBOL OpAmps\\opamp2 8 -488 R0
SYMATTR InstName U7
SYMATTR Value 2TL081
SYMBOL pnp 152 -376 M180
SYMATTR InstName 22N3906
SYMBOL res 200 -600 R0
SYMATTR InstName R13
SYMATTR Value 0.5k
SYMBOL voltage -936 -232 R0
SYMATTR InstName V1
SYMATTR Value 30
SYMBOL voltage -808 -232 R0
SYMATTR InstName V2
SYMATTR Value 12
SYMBOL OpAmps\\opamp2 712 24 R0
SYMATTR InstName U1
SYMATTR Value 2TL081
SYMBOL res 664 8 R90
SYMATTR InstName Rt_g1
SYMATTR Value 5.6k
SYMBOL res 792 8 R90
SYMATTR InstName Rt_f
SYMATTR Value 10k
SYMBOL res 504 -72 R0
SYMATTR Value 680
SYMATTR InstName Rt_1
SYMBOL res 504 24 R0
SYMATTR InstName Rt_g2
SYMATTR Value 620