* SPICE netlist
Q1 N001 3 N008 0 NP
Q2 N001 2 N009 0 NP
Q5 N011 N010 N009 0 PN
Q6 N013 N010 N008 0 PN
Q7 N013 N016 N018 0 NP
Q8 N011 N016 N019 0 NP
Q3 7 N013 N016 0 NP
Q4 N001 N001 7 0 PN
R1 N018 4 1K
R2 N016 4 50K
R3 N019 4 1K
Q9 N010 N001 7 0 PN
Q10 N002 N002 7 0 PN
Q11 N003 N002 7 0 PN
Q12 N014 N014 4 0 NP
Q13 N010 N014 N020 0 NP
R4 N020 4 5K
Q14 N003 N004 N007 0 NP
Q15 N007 N015 N017 0 NP
Q16 N007 N011 N015 0 NP
R5 N015 4 50K
R6 N017 4 50
Q17 N011 N017 4 0 NP
C1 N003 N011 30p
R7 N007 N004 7.5K
R8 N003 N004 4.5K
Q18 7 N003 N005 0 NP
Q19 4 N007 N012 0 PN
R9 N005 6 25
R10 6 N012 50
Q20 N003 N005 6 0 NP
V1 4 0 -15
V2 7 0 15
R11 6 2 10K
R12 2 0 1K
V3 N006 0 SINE(0 1 1K)
R13 N002 N014 39K
R14 3 N006 10K
.tran 10m

* LTspice schematic (.asc)
Version 4
SHEET 1 1728 1072
WIRE 16 -520 -656 -520
WIRE 864 -520 96 -520
WIRE -544 -440 -784 -440
WIRE -368 -440 -544 -440
WIRE -304 -440 -368 -440
WIRE -112 -440 -304 -440
WIRE 48 -440 -112 -440
WIRE 416 -440 48 -440
WIRE 640 -440 416 -440
WIRE -784 -424 -784 -440
WIRE -304 -408 -304 -440
WIRE -112 -408 -112 -440
WIRE 48 -408 48 -440
WIRE 416 -408 416 -440
WIRE -224 -360 -240 -360
WIRE -176 -360 -224 -360
WIRE 128 -360 112 -360
WIRE 352 -360 128 -360
WIRE -784 -328 -784 -344
WIRE 640 -328 640 -440
WIRE 48 -280 48 -312
WIRE 128 -280 128 -360
WIRE 128 -280 48 -280
WIRE 416 -280 416 -312
WIRE 416 -280 160 -280
WIRE 528 -280 416 -280
WIRE 576 -280 528 -280
WIRE -784 -248 -832 -248
WIRE -656 -248 -656 -520
WIRE -656 -248 -704 -248
WIRE -544 -248 -656 -248
WIRE -144 -248 -544 -248
WIRE 528 -232 528 -280
WIRE -304 -216 -304 -312
WIRE -304 -216 -464 -216
WIRE -224 -216 -224 -360
WIRE -224 -216 -304 -216
WIRE 304 -216 288 -216
WIRE 416 -216 416 -280
WIRE 416 -216 384 -216
WIRE 416 -184 416 -216
WIRE 640 -184 640 -232
WIRE 640 -184 592 -184
WIRE -464 -168 -464 -216
WIRE -224 -168 -224 -216
WIRE 48 -168 48 -280
WIRE 640 -152 640 -184
WIRE 288 -136 288 -216
WIRE 352 -136 288 -136
WIRE -768 -120 -864 -120
WIRE -544 -120 -688 -120
WIRE -528 -120 -544 -120
WIRE -144 -120 -144 -248
WIRE -144 -120 -160 -120
WIRE 160 -88 160 -280
WIRE -864 -72 -864 -120
WIRE 288 -72 288 -136
WIRE 304 -72 288 -72
WIRE 416 -72 416 -88
WIRE 416 -72 384 -72
WIRE -464 -40 -464 -72
WIRE -224 -40 -224 -72
WIRE 528 -40 528 -136
WIRE 640 -40 640 -72
WIRE 640 -40 528 -40
WIRE 736 -40 640 -40
WIRE 864 -40 864 -520
WIRE 864 -40 736 -40
WIRE 640 -24 640 -40
WIRE -288 8 -400 8
WIRE -112 8 -112 -312
WIRE -112 8 -288 8
WIRE 416 8 416 -72
WIRE 416 8 272 8
WIRE 272 24 272 8
WIRE -864 56 -864 8
WIRE -368 56 -368 -440
WIRE -224 72 -224 56
WIRE 160 72 160 -24
WIRE 160 72 -224 72
WIRE 208 72 160 72
WIRE 640 72 640 56
WIRE -464 104 -464 56
WIRE -432 104 -464 104
WIRE 416 120 416 8
WIRE 576 120 416 120
WIRE 416 152 416 120
WIRE -464 184 -464 104
WIRE -224 184 -224 72
WIRE 48 184 48 -88
WIRE 48 184 -32 184
WIRE 272 200 272 120
WIRE 352 200 272 200
WIRE -112 216 -112 8
WIRE 48 216 48 184
WIRE -368 232 -368 152
WIRE -368 232 -400 232
WIRE -288 232 -368 232
WIRE 160 232 160 72
WIRE -32 264 -32 184
WIRE -32 264 -48 264
WIRE -16 264 -32 264
WIRE 416 280 416 248
WIRE 416 280 224 280
WIRE -464 312 -464 280
WIRE -368 312 -368 232
WIRE -224 312 -224 280
WIRE 272 312 272 200
WIRE 416 312 416 280
WIRE -112 328 -112 312
WIRE -544 424 -688 424
WIRE -464 424 -464 392
WIRE -464 424 -544 424
WIRE -368 424 -368 392
WIRE -368 424 -464 424
WIRE -224 424 -224 392
WIRE -224 424 -368 424
WIRE -112 424 -112 408
WIRE -112 424 -224 424
WIRE 48 424 48 312
WIRE 48 424 -112 424
WIRE 160 424 160 328
WIRE 160 424 48 424
WIRE 272 424 272 392
WIRE 272 424 160 424
WIRE 416 424 416 392
WIRE 416 424 272 424
WIRE 640 424 640 168
WIRE 640 424 416 424
WIRE -688 440 -688 424
WIRE -688 536 -688 520
FLAG -544 -120 3
FLAG -544 -248 2
FLAG -688 536 0
FLAG 736 -40 6
FLAG -784 -328 0
FLAG -832 -248 0
FLAG -864 56 0
FLAG -544 -440 7
FLAG -544 424 4
SYMBOL NPN -528 -168 R0
SYMATTR InstName Q1
SYMATTR Value NP
SYMBOL npn -160 -168 M0
SYMATTR InstName Q2
SYMATTR Value NP
SYMBOL PNP -288 56 M180
SYMATTR InstName Q5
SYMATTR Value PN
SYMBOL pnp -400 56 R180
SYMATTR InstName Q6
SYMATTR Value PN
SYMBOL npn -400 184 M0
SYMATTR InstName Q7
SYMATTR Value NP
SYMBOL npn -288 184 R0
SYMATTR InstName Q8
SYMATTR Value NP
SYMBOL npn -432 56 R0
SYMATTR InstName Q3
SYMATTR Value NP
SYMBOL pnp -240 -312 R180
SYMATTR InstName Q4
SYMATTR Value PN
SYMBOL RES -480 296 R0
SYMATTR InstName R1
SYMATTR Value 1K
SYMBOL res -384 296 R0
SYMATTR InstName R2
SYMATTR Value 50K
SYMBOL res -240 296 R0
SYMATTR InstName R3
SYMATTR Value 1K
SYMBOL pnp -176 -312 M180
SYMATTR InstName Q9
SYMATTR Value PN
SYMBOL pnp 112 -312 R180
SYMATTR InstName Q10
SYMATTR Value PN
SYMBOL pnp 352 -312 M180
SYMATTR InstName Q11
SYMATTR Value PN
SYMBOL npn -16 216 R0
SYMATTR InstName Q12
SYMATTR Value NP
SYMBOL npn -48 216 M0
SYMATTR InstName Q13
SYMATTR Value NP
SYMBOL res -128 312 R0
SYMATTR InstName R4
SYMATTR Value 5K
SYMBOL npn 352 -184 R0
SYMATTR InstName Q14
SYMATTR Value NP
SYMBOL npn 352 152 R0
SYMATTR InstName Q15
SYMATTR Value NP
SYMBOL npn 208 24 R0
SYMATTR InstName Q16
SYMATTR Value NP
SYMBOL res 256 296 R0
SYMATTR InstName R5
SYMATTR Value 50K
SYMBOL res 400 296 R0
SYMATTR InstName R6
SYMATTR Value 50
SYMBOL npn 224 232 M0
SYMATTR InstName Q17
SYMATTR Value NP
SYMBOL cap 144 -88 R0
SYMATTR InstName C1
SYMATTR Value 30p
SYMBOL res 400 -88 R90
SYMATTR InstName R7
SYMATTR Value 7.5K
SYMBOL res 400 -232 R90
SYMATTR InstName R8
SYMATTR Value 4.5K
SYMBOL npn 576 -328 R0
SYMATTR InstName Q18
SYMATTR Value NP
SYMBOL pnp 576 168 M180
SYMATTR InstName Q19
SYMATTR Value PN
SYMBOL res 624 -168 R0
SYMATTR InstName R9
SYMATTR Value 25
SYMBOL res 624 -40 R0
SYMATTR InstName R10
SYMATTR Value 50
SYMBOL npn 592 -232 M0
SYMATTR InstName Q20
SYMATTR Value NP
SYMBOL VOLTAGE -688 424 R0
SYMATTR InstName V1
SYMATTR Value -15
SYMBOL voltage -784 -440 R0
SYMATTR InstName V2
SYMATTR Value 15
SYMBOL res 112 -536 R90
SYMATTR InstName R11
SYMATTR Value 10K
SYMBOL res -688 -264 R90
SYMATTR InstName R12
SYMATTR Value 1K
SYMBOL voltage -864 -88 R0
SYMATTR InstName V3
SYMATTR Value SINE(0 1 1K)
SYMBOL res 32 -184 R0
SYMATTR InstName R13
SYMATTR Value 39K
SYMBOL res -672 -136 R90
SYMATTR InstName R14
SYMATTR Value 10K