* SPICE netlist
V1 COM 0 6V
V2 FREF 0 PULSE(0 6 0 0.00000001 0.00000001 0.0000045 0.000005)
Cant ANT 0 8pF
Chand ANT 0 {Chand}
R1 COM ANT 330000
D3 ANT COM D
D4 0 ANT D
C6 COM ANT 1.5pF
C7 ANT 0 1.5pF
XU2 0 FREF OUT COM N001 ANT ANT COM NE555 ;pnba GND)TRIG)OUT)RST)CV)THRS)DIS)Vcc
C1 N001 0 1nF
Cant1 ANT2 0 8pF
Chand1 ANT2 0 {Chand}
R2 ANT2 COM 500000
XU1 0 FREF OUT2 COM N006 ANT2 ANT2 COM NE555 ;pnba GND)TRIG)OUT)RST)CV)THRS)DIS)Vcc
C2 N006 0 1nF
Q1 N004 0 COM 0 2N3906
R4 0 N004 1500
Q2 N005 N003 N002 0 2N3906
R5 N002 COM 200000
R3 ANT2 N005 20000
R6 FREF N003 200000
.tran 0 0.000333 0.0003 0.000000001 startup
.step param Chand list 0pF 0.1pF 0.2pF 0.3pF 0.4pF 0.5pF 0.6pF 0.7pF 0.8pF 0.9pF 1pF 1.1pF 1.2pF 1.3pF 1.4pF 1.5pF
.MEAS TRAN res1 FIND V(out) AT=1m

* LTspice schematic (.asc)
Version 4
SHEET 1 2128 1888
WIRE 632 -880 632 -944
WIRE 632 -880 584 -880
WIRE -888 -832 -920 -832
WIRE 584 -832 584 -880
WIRE 632 -832 632 -880
WIRE -1064 -800 -1064 -848
WIRE 584 -736 584 -768
WIRE 632 -736 632 -768
WIRE 632 -736 584 -736
WIRE 712 -736 632 -736
WIRE 584 -704 584 -736
WIRE 632 -704 632 -736
WIRE -1064 -688 -1064 -720
WIRE -920 -672 -920 -832
WIRE 584 -608 584 -640
WIRE 632 -608 632 -640
WIRE 632 -608 584 -608
WIRE -920 -560 -920 -592
WIRE 632 -560 632 -608
WIRE -264 -368 -328 -368
WIRE 24 -368 -40 -368
WIRE -264 -304 -680 -304
WIRE 72 -304 -40 -304
WIRE 184 -304 72 -304
WIRE 328 -304 264 -304
WIRE -264 -240 -680 -240
WIRE 72 -240 72 -304
WIRE 72 -240 -40 -240
WIRE 488 -240 488 -320
WIRE 488 -240 72 -240
WIRE 568 -240 488 -240
WIRE -264 -176 -328 -176
WIRE 8 -176 -40 -176
WIRE 488 -160 488 -240
WIRE 568 -160 568 -240
WIRE 8 -144 8 -176
WIRE 8 -48 8 -80
WIRE 488 -32 488 -96
WIRE 568 -32 568 -96
WIRE 392 288 392 208
WIRE 1048 400 1048 352
WIRE 392 464 392 368
WIRE -456 512 -552 512
WIRE 328 512 -376 512
WIRE 184 544 184 336
WIRE 1048 544 1048 496
WIRE -264 608 -328 608
WIRE 24 608 -40 608
WIRE 392 608 392 560
WIRE -552 672 -552 512
WIRE -552 672 -680 672
WIRE -264 672 -552 672
WIRE 184 672 184 624
WIRE 184 672 -40 672
WIRE 1048 688 1048 624
WIRE -264 736 -680 736
WIRE 184 736 184 672
WIRE 184 736 -40 736
WIRE 392 736 392 688
WIRE 392 736 184 736
WIRE 568 736 568 656
WIRE 568 736 392 736
WIRE 648 736 568 736
WIRE -264 800 -328 800
WIRE 8 800 -40 800
WIRE 568 816 568 736
WIRE 648 816 648 736
WIRE 8 832 8 800
WIRE 8 928 8 896
WIRE 568 944 568 880
WIRE 648 944 648 880
FLAG -1064 -688 0
FLAG -888 -832 FREF
IOPIN 224 -48 Out
FLAG -920 -560 0
FLAG 488 -320 ANT
FLAG 488 -32 0
FLAG 568 -32 0
FLAG -680 -304 FREF
IOPIN 432 480 In
FLAG -1064 -848 COM
FLAG 632 -560 0
FLAG 632 -944 COM
FLAG 712 -736 ANT
FLAG 24 -368 COM
FLAG -328 -368 0
FLAG -328 -176 COM
FLAG 8 -48 0
FLAG 328 -304 COM
FLAG -680 -240 OUT
FLAG 568 656 ANT2
FLAG 568 944 0
FLAG 648 944 0
FLAG -680 672 FREF
IOPIN 432 1456 In
FLAG 24 608 COM
FLAG -328 608 0
FLAG -328 800 COM
FLAG 8 928 0
FLAG -680 736 OUT2
FLAG 1048 688 0
FLAG 1048 352 COM
FLAG 984 448 0
FLAG 392 208 COM
FLAG 184 336 COM
SYMBOL voltage -1064 -816 R0
SYMATTR InstName V1
SYMATTR Value 6V
SYMBOL voltage -920 -688 R0
SYMATTR InstName V2
SYMATTR Value PULSE(0 6 0 0.00000001 0.00000001 0.0000045 0.000005)
SYMBOL cap 472 -160 R0
SYMATTR InstName Cant
SYMATTR Value 8pF
SYMBOL cap 552 -160 R0
SYMATTR InstName Chand
SYMATTR Value {Chand}
SYMBOL res 280 -320 R90
SYMATTR InstName R1
SYMATTR Value 330000
SYMBOL diode 600 -768 R180
SYMATTR InstName D3
SYMBOL diode 600 -640 R180
SYMATTR InstName D4
SYMBOL cap 616 -832 R0
SYMATTR InstName C6
SYMATTR Value 1.5pF
SYMBOL cap 616 -704 R0
SYMATTR InstName C7
SYMATTR Value 1.5pF
SYMBOL NE555 -152 -272 R0
SYMATTR InstName U2
SYMBOL cap -8 -144 R0
SYMATTR InstName C1
SYMATTR Value 1nF
SYMBOL cap 552 816 R0
SYMATTR InstName Cant1
SYMATTR Value 8pF
SYMBOL cap 632 816 R0
SYMATTR InstName Chand1
SYMATTR Value {Chand}
SYMBOL res 200 640 R180
SYMATTR InstName R2
SYMATTR Value 500000
SYMBOL NE555 -152 704 R0
SYMATTR InstName U1
SYMBOL cap -8 832 R0
SYMATTR InstName C2
SYMATTR Value 1nF
SYMBOL pnp 984 496 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL res 1064 640 R180
SYMATTR InstName R4
SYMATTR Value 1500
SYMBOL pnp 328 560 M180
SYMATTR InstName Q2
SYMATTR Value 2N3906
SYMBOL res 408 384 R180
SYMATTR InstName R5
SYMATTR Value 200000
SYMBOL res 408 704 R180
SYMATTR InstName R3
SYMATTR Value 20000
SYMBOL res -472 528 R270
SYMATTR InstName R6
SYMATTR Value 200000