Adding random noise to a power supply?

[Mike Rocket J. Squirrel E]

What might be a handy way to add arbitrary amounts of random noise to
various DC power supplies in a simulation to observe how the powered
circuit handles it? I'm running LTSpice.

--
Mike "Rocket J Squirrel" Elliott

 

[Mike Engelhardt]

Mike,

What might be a handy way to add arbitrary amounts of random noise to
various DC power supplies in a simulation to observe how the powered
circuit handles it? I'm running LTSpice.

If your doing a .noise analysis, just put a resistor
to ground and across the input to a linear voltage
dependent voltage source. Then put the output nodes
of this voltage source in series with the power supply.

If your doing a .tran analysis, you can put a behavioral
voltage source in series. Give this source a value
of "V=random(100K*time)" for a noise voltage that
varies randomly between 0V and 1V at a period of
10us. You will have to stipulate a maximum timestep
for the waveform to look right. This is not the
kind of noise you'd expect from any physically stochastic
process, but you can do Fourier analysis to see what the
noise density really was with this critter.

--Mike