Version 4
SHEET 1 880 680
WIRE 208 0 48 0
WIRE 48 48 48 0
WIRE 48 160 48 128
WIRE 208 240 48 240
WIRE 320 240 272 240
WIRE 384 240 320 240
WIRE 320 272 320 240
WIRE 48 288 48 240
WIRE 48 400 48 368
WIRE 320 400 320 352
FLAG 48 160 0
FLAG 208 0 DR1
FLAG 320 400 0
FLAG 384 240 out
FLAG 48 400 0
SYMBOL voltage 48 32 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value PULSE(-1 1 0 {1/freq} {1/freq} 0 {2/freq})
SYMBOL res 304 256 R0
SYMATTR InstName R1
SYMATTR Value 4.7k
SYMBOL cap 272 224 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL bv 48 272 R0
SYMATTR InstName B1
SYMATTR Value V=100*V(DR1)
TEXT 56 -104 Left 2 !.tran 0 0.05 0 10u
TEXT 56 -160 Left 2 !.param freq=100
TEXT 56 -72 Left 2 !.options plotwinsize=0