Physics 536 - Spring 2008

Electronic Techniques for Research

Yet Another Example of Using Berkeley SPICE with nanoHUB

Example of square wave shaping by a low-pass filter:

Consider the circuit shown below:
In which the components have the following values:
ComponentValue
Vin(t) +- 1 V square wave, f=250 kHz
L 10 μH
R 63 Ω
The circuit forms a low-pass filter with a cutoff frequency of ω-3 db = R/L = 2&pi f -3 db, where f -3 db = 1 MHz.

SPICE netlist

The voltage source is described using the format 
  VIN <N+> <N-> PULSE(V1 V2 TD TR TF PW PER)
in which the parameters have the following meaning:
V1 initial voltage (volts)
V2 pulsed voltage (volts)
TD delay time (seconds)
TR rise time (seconds)
TF fall time (seconds)
PW pulse width (seconds)
PER period of waveform (seconds)
In this case, if we simulate the circuit over 8 μs, the netlist will be

and the output waveform will be the following: