Spectrum Software
Industrial Strength Simulation




Spectrum Software has released Micro-Cap 11, the eleventh generation of our SPICE circuit simulator.

For users of previous Micro-Cap versions, check out the new features available in the latest version. For those of you who are new to Micro-Cap, take our features tour to see what Micro-Cap has to offer.




Gyrator Macro


The gyrator is a two port network that is designed to transform a load impedance into an input impedance where the input impedance is proportional to the inverse of the load impedance. The gyrator network can be used to transform a load capacitance into an inductance. This feature is extremely useful in integrated circuit technology where it is nearly impossible to realize physical inductors. The gyrator circuit can be created with just two dependent sources. The figure below displays the schematic of the gyrator macro.

Gyrator Macro
The gyrator macro consists of just two VofI sources. There is only one parameter in this macro: g. The g parameter defines the gyrator ratio and is used to calculate the gain of the dependent sources. Each source uses the current through the other source as its input. The H1 source has a negative gain because its current input is actually the negative value of the current through H2, and the negative gain will give the two sources the correct opposite polarities.

The test schematic compares two equivalent circuits: one using an inductor and one using a gyrator and a capacitor. The equation for a gyrator transforming a capacitor to an inductor is as follows:


The 100nF capacitor and gyrator should produce the same output as a 1mH inductor.

As can be seen in the figure below, the AC output of the gain and the phase for both circuits produce the same results.

Gyrator Macro Analysis
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