Version 4
SHEET 1 2220 784
WIRE -192 112 -480 112
WIRE 176 112 -192 112
WIRE -336 128 -416 128
WIRE -544 160 -592 160
WIRE -416 160 -416 128
WIRE -368 160 -416 160
WIRE -272 160 -304 160
WIRE -176 160 -240 160
WIRE 176 160 176 112
WIRE 176 160 48 160
WIRE -592 192 -592 160
WIRE -480 208 -528 208
WIRE -480 224 -480 208
WIRE -272 224 -272 160
WIRE -176 224 -272 224
WIRE 80 224 48 224
WIRE -528 256 -528 208
WIRE -512 256 -528 256
WIRE -416 256 -416 160
WIRE -416 256 -448 256
WIRE -368 256 -416 256
WIRE -272 256 -272 224
WIRE -272 256 -304 256
WIRE 176 272 176 160
WIRE -592 288 -592 272
WIRE -288 288 -592 288
WIRE -176 288 -288 288
WIRE 80 288 48 288
WIRE -272 320 -272 256
WIRE -272 320 -320 320
WIRE -416 336 -416 256
WIRE -320 336 -320 320
WIRE -192 352 -192 112
WIRE -176 352 -192 352
WIRE 112 352 48 352
WIRE -272 384 -272 320
WIRE 80 384 80 288
WIRE 80 384 -272 384
WIRE 176 384 176 352
WIRE 176 384 144 384
WIRE 144 400 144 384
WIRE -320 432 -320 400
WIRE -240 432 -240 160
WIRE -240 432 -320 432
WIRE 112 432 112 416
WIRE 112 432 -240 432
WIRE 176 432 176 384
WIRE 176 432 112 432
FLAG 144 400 0
FLAG -288 288 Out
IOPIN -288 288 Out
FLAG 80 224 Od
IOPIN 80 224 Out
FLAG -416 336 Od
IOPIN -416 336 In
SYMBOL cap -304 400 R180
WINDOW 0 24 54 Left 0
WINDOW 3 24 8 Left 0
SYMATTR InstName Ct
SYMATTR Value 1n
SYMATTR SpiceLine V=50v
SYMBOL diode -368 240 M90
WINDOW 0 50 -5 VBottom 0
WINDOW 3 -34 33 Invisible 0
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL Pote -544 240 M90
WINDOW 123 85 67 VCenter 0
WINDOW 3 91 59 Invisible 0
WINDOW 0 65 37 VRight 0
SYMATTR Value2 set=mark
SYMATTR Value rt=pot
SYMATTR InstName mark
SYMBOL 555_ALL -16 272 R0
WINDOW 38 -83 78 Left 0
SYMATTR InstName U1
SYMBOL cap 128 416 R180
WINDOW 0 72 11 Left 0
WINDOW 3 24 8 Left 0
SYMATTR InstName Cbp
SYMATTR Value 10n
SYMATTR SpiceLine V=50v
SYMBOL Pote -400 144 M90
WINDOW 123 78 56 VCenter 0
WINDOW 3 72 64 Invisible 0
WINDOW 0 50 32 VRight 0
SYMATTR Value2 set=mark
SYMATTR Value rt=pot
SYMATTR InstName space
SYMBOL voltage 176 256 R0
WINDOW 0 -51 22 Left 0
WINDOW 3 -29 58 Left 0
SYMATTR InstName V+
SYMATTR Value {Vdd}
SYMBOL npn2 -544 112 R0
WINDOW 0 -24 27 Left 0
WINDOW 3 21 50 Left 0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL res -608 176 R0
SYMATTR InstName R1
SYMATTR Value 10k
TEXT -136 128 Left 0 !.tran {(mark+.1)*pot/1e7}
TEXT -496 488 Left 0 !.params: Vdd 15 Ronx=.1 pot=91k\n.step param mark .01 .99 .49\n.meas tran ta FIND time WHEN V(out)={Vdd/2} td=.1m rise=1\n.meas tran tb FIND time WHEN V(out)={Vdd/2} td=.1m rise=11\n.meas tran Frec PARAM 10/(tb-ta)\n.Meas tran Tc FIND time WHEN V(Out)={Vdd/2} td=.1m fall=1\n.Meas tran Td FIND time WHEN V(Out)={Vdd/2} td=.1m fall=2\n.Meas tran T1 Param  (Tc-Ta)\n.Meas tran T2  Param  (Td-Ta)\n.Meas tran Ton Param If (T1>0, T1, T2)\n.Meas tran Duty% Param  Ton*Frec*100