
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 ...