Short pulse from a step

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Pulse generator from a step input: Q1 inverts the step, C1 pushes Q2's base negative so Q2 turns off for about 0.7·R3·C1, producing a short positive pulse at the output.

Parts

Picture

Simulation

This circuit is set up for a transient (time domain) analysis: .tran 0 2m 0 1u. Run it in your browser, change values and see the waveforms update.

SPICE netlist

* Short pulse from a step - Main
.param Ct=100n
V1 in 0 PULSE(0 5 50u 100n 100n 1 2)
R1 in n001 10k
Q1 n002 n001 0 2N3904
R2 vcc n002 1k
C1 n002 base {Ct}
R3 vcc base 10k
Q2 out base 0 2N3904
R4 vcc out 1k
V2 vcc 0 5
.model 2N3904 NPN(Is=6.734f Xti=3 Eg=1.11 Vaf=74.03 Bf=416.4 Ne=1.259 Ise=6.734f Ikf=66.78m Xtb=1.5 Br=.7371 Nc=2 Isc=0 Ikr=0 Rc=1 Cjc=3.638p Mjc=.3085 Vjc=.75 Fc=.5 Cje=4.493p Mje=.2593 Vje=.75 Tr=239.5n Tf=301.2p Rb=10)
.meas tran tpw TRIG V(out) VAL=2.5 RISE=1 TARG V(out) VAL=2.5 FALL=1
.meas tran tpred PARAM 0.693*10k*Ct
.meas tran vbmin MIN V(base)
.tran 0 2m 0 1u
.end