|Created||July 12, 2012|
|Last modified||July 12, 2012|
|Tags||behavioral device-modeling diode|
A behavioral current source can be used to model an "ideal" piecewise-linear diode, conducting in one direction but not the other.
In response to Create circuit from current–voltage characteristic:
The current source I1 is programmed with the expression "MAX(0, V()/0.1)". This means that at every point in time, it will evaluate the voltage across itself (divided by 0.1), and compare to 0, taking the higher of the two.
Effectively, this means that when the voltage is positive, it will conduct current equal to the voltage drop divided by 0.1, i.e. it looks exactly like a 0.1 ohm resistor. When the applied voltage is negative, the current becomes zero.
Scale and offset can be applied to put the knee exactly where desired.
Run the DC Sweep simulation to see the I-V characteristic curve. Or run a time-domain simulation to see what happens when you put a sine wave across it.
You can copy+paste the behavioral current source into another circuit and effectively use it as a diode!
Now that is very neat.
I've tried various ways to make 'ideal' diodes but I'd not thought of such a simple solution.
One caution though: beware that these Piecewise-linear Diode (Behavioral Sources) models may cause convergence problems because they have discontinuous derivatives (which simulators don't generally like). Placing a large resistance and a small capacitance in parallel across them may help.
July 12, 2012
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