Short pulse from a step or pulse

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Pulse generator from a step or short pulse (Art of Electronics Fig. 2.12): Q3 and R5 feed the output back to hold Q1's collector low, so the output pulse width (about 0.7·R3·C1) is independent of the input pulse width.

Parts

Picture

Simulation

This circuit is set up for a transient (time domain) analysis: .tran 0 300u 0 0.5u. Run it in your browser, change values and see the waveforms update.

SPICE netlist

* Short pulse from a step or pulse - Main
.param Ct=10n
.param tin=10u
V1 in 0 PULSE(0 5 50u 100n 100n {tin} 1)
R1 in n001 10k
Q1 c1 n001 0 2N3904
R2 vcc c1 1k
C1 c1 b2 {Ct}
R3 vcc b2 10k
Q2 out b2 0 2N3904
R4 vcc out 1k
V2 vcc 0 5
Q3 c1 n002 0 2N3904
R5 n002 out 20k
.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 vb2min MIN V(b2)
.tran 0 300u 0 0.5u
.end