Analog Electronics

Tncks of the trade 283

Synthetic inductors

With filters, as with so many other electronic

circuits, there is more than one way of achieving

the desired result. Instead of avoiding inductors by

taking the FDNR approach, we could equally well

stick with type 1 devices (Figure 11.4a) but realize

them with opamps, resistors and capacitors.

Figure 11.7 shows a synthetic inductor which has

appeared a number of times in the literature.^ Like

the FDNRs we saw earlier, it has one end tied to

ground. This inductor can be used in high-pass

filters, be they Butterworth, Chebyshev or elliptic.

Figure 11.7a shows the circuit dimensioned to give

a 1 Η inductor ...