A structure that Collier patented for simulating monodirectional impedances is shown in Figure 3(b), below.
Provided that the currents in the two inputs on the left of the active device are negligible, it is then sufficient to design the active device to produce the output potential V satisfying
This insures that the current in the output impedance Z0 is equal to the current desired in the simulated impedance. Thus, given the desired impedance Zsim and any convenient impedance Z0, the designer needs only design the active device such that its output potential V satisfies the foregoing condition. Solving for this critical value:
Such active devices are easily devised using conventional operational voltage amplifiers, but of course, a little ingenuity never hurts either.
This method of impedance simulation is patented under United States Patent 4,963,845, and the simulating structure is likewise patented therein.