Simulating varicap diode in LTSpice

Question

I have been looking into making a voltage controlled oscillator using varicap diodes, however I have had hard time simulating the diodes in spice.

Would anyone here have an idea how this would be done?

Thanks in advance

Diode models have baseline capacitance and exponent used in the reverse-voltage effect on capacitance. — analogsystemsrf, Sep 17 '17 at 02:32
Have you tried searching the net for (your) models to see if they work? — a concerned citizen, Sep 17 '17 at 05:55

score 2 · Answer 1 · edited Jun 11 '20 at 15:10

2

Maybe you can solve your problem by using variable capacitance models (intially found on the LTSpice Yahoo group I think ).

The equation governing the charge and voltage of a capacitor is \begin{equation} Q = CV \end{equation} In LTSpice, you cannot change the capacitance value. Rather you specify the charge of the capacitor. Hence, you specify your capacitor value as: \begin{equation} q = V{(\text{your capacitance node})} \cdot x \end{equation} where x is the voltage over the capacitor in question. This is covered in the LTSpice Help file under C. Capacitor

edited Jun 11 '20 at 15:10

Community

1

answered Nov 27 '19 at 10:35

ocspro

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I believe ocspro's solution does not respect conservation of charge. I advise reading this short article: https://designers-guide.org/modeling/varactors.pdf – propaganda Apr 05 '22 at 04:41

Simulating varicap diode in LTSpice

1 Answers1