TABLE OF CONTENTS Thanks to their particular characteristics, CCIIs can be widely used in the implementation of circuits able to convert impedances. Negative impedances converters in general, and FDNR (Frequency Dependent Negative Resistance) in particular, are usually implemented by CCIIs instead of op-amps because of their better performance.
In figure 5.15 a simple CCII-based negative impedance converter has been reported [2].
Using a positive CCII, the current injected at X node will flow into Z impedance, so imposing a negative voltage at Y node. This value is also present at X node, where the equivalent impedance is equal to ?Z, as shown in eq. (5.14).
If we consider, as a source, a voltage generator instead of a current generator, the solution presented in figure 5.16 can be employed, where the equivalent impedance at Y node is now considered.
The operating principle is exactly the same and the resulting input impedance at input node Y is still equal to ?Z.
The two solutions proposed in figure 5.15 and 5.16 allow the simulation of a grounded negative impedance. In order to implement a floating negative impedance, it is necessary to introduce a second CCII. A possible implementation is reported in figure 5.17. We notice that this topology has been obtained simply doubling that shown in figure 5.16, so the resulting input impedance is still equal to ?Z.
Using CCIIs, it is...
