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[Moved]: What is TRAP ringing

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raghavkmr

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I am simulating an Ip using mentor's eldo
it shows

warning "Possible TRAP ringing has been detected during transient simulation at time=4.746029e+04."
 

SunnySkyguy

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Re: What is trap ringing

when using forward Euler on stiff circuits the timestep must be chosen small relative to the fastest time constant to avoid stability problems.
 

erikl

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See here for more info:

From: Ken Kundert: Modeling Varactors p. 3 of 7

The essential point to take away is that with models formulated using (3) the charge must be estimated from the capacitance. There are different ways of doing the estimation. The backward Euler approximation given above estimates the change in charge from the capacitance at the end of the step; forward Euler uses the capacitance at the beginning of the step, and trapezoidal rule uses a combination. Each produces an error that grows with the time step that causes charge to not be conserved. With models formulated using (2) the charge is computed explicitly, so there is no approximation.

View attachment Integration_methods.pdf

Try the GEAR method.
 

dick_freebird

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TRAPezoidal numerical method has no damping and will
often be seen to "sawtooth" between upper and lower
tolerance limits. This, with any subsequent gain, can
make for unrealistic behaviors in the circuit, a transient
noise of sorts with consequences TBD.
 

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