Simple T-line ngpsice sim *square wave source Vin vin 0 PULSE(10 1.0 0 1n 1n 20e

Question

Simple T-line ngpsice sim

*square wave source  
Vin vin 0 PULSE(10 1.0 0 1n 1n 20e-9 40e-9)

*source impedance
rsrc vin rsrc_out 50

vtest rsrc_out tline_in 0 ; voltage source to measure current

t1 tline_in 0 tline_out 0 z0=50 td=5ns ; a 5ns long, 50 ohm, T-line

rload tline_out 0 1G ; termination at end of line

.control

set color0=white
set color1=black
tran 100ps 40ns ; transient simulation, 100ps steps for 40ns
plot v(tline_in) v(tline_out) xl 1ns 30ns ; plot T-line input and output
plot i(vtest) xl 1ns 30ns ; plot current at T-line input

.endc

.end

Modify 'Vin' so that the fall time is 100psec. What is the flight time of the transmission line?

Explanation / Answer

*square wave source  
Vin vin 0 PULSE(10 1.0 0 1n 100p 20e-9 40e-9)

*source impedance
rsrc vin rsrc_out 50

vtest rsrc_out tline_in 0 ; voltage source to measure current

t1 tline_in 0 tline_out 0 z0=50 td=5ns ; a 5ns long, 50 ohm, T-line

rload tline_out 0 1G ; termination at end of line

.control

set color0=white
set color1=black
tran 100ps 40ns ; transient simulation, 100ps steps for 40ns
plot v(tline_in) v(tline_out) xl 1ns 30ns ; plot T-line input and output
plot i(vtest) xl 1ns 30ns ; plot current at T-line input

.endc

.end

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