2.5 Four-Terminal Networks

Chapter 2.5 Four-Terminal Networks

Physics Lecture Notes – Phys 395 Electronics Book
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Physics Lecture Notes – Phys 395 Electronics Book

  • CHAPTER 2. ALTERNATING CURRENT CIRCUITS40Table 2.1: Numerical values for example circuit.ω(rad/s)log10 ω|Zeq|log10 |Zeq|1(100)010111011102210221/√2× 1032.81033103310441/√2× 1032.810551022106610112.5Four-Terminal NetworksOur previous resonance circuit is an example of a two-terminal network. A source is presentbut no load.A four-terminal network also has the source removed.The four-terminalnetwork can be described by a transfer function. A generic four-terminal network is shownin figure 2.17. Such a circuit can be analyzed simply by considering it as a voltage divider.In generalH =Z2Z1 + Z2.(2.114)2.6Single-Term Approximations of HA circuit with a few components quickly leads to a complicated expression for the transferfunction. It is often sufficient, and of course, easier to work with approximations to thetransfer function.Let H be the ratio of two polynomialsH(jω)=P(jω)Q(jω),(2.115)whereP(jω)=Ni=0Pi(jω)iandQ(jω)=Mk=0Qk(jω)k .(2.116)If one term dominates in each polynomialP(jω)≈ Pn(jω)nandQ(jω)≈ Qm(jω)m.(2.117)Thus