. The Bell System technical journal . Fig. 2--Transistor mechanism. is a rectitier biased stiongly in the low-conducting direction. It therefore hasa rectifying barrier in the germanium near it, which causes the collectorimpedance to be high. However, the collector can be influenced by the 370 BELL SYSTEM TECHNICAL JOURNAL emitter if the latter is arranged to emit anomalous charge carriers, thatis, carriers of the sign not normally present in the interior of the material. Circuits As has been explained by liardecn, Bratlain, and Shockley, many featuresof the transistor are nicely
. The Bell System technical journal . Fig. 2--Transistor mechanism. is a rectitier biased stiongly in the low-conducting direction. It therefore hasa rectifying barrier in the germanium near it, which causes the collectorimpedance to be high. However, the collector can be influenced by the 370 BELL SYSTEM TECHNICAL JOURNAL emitter if the latter is arranged to emit anomalous charge carriers, thatis, carriers of the sign not normally present in the interior of the material. Circuits As has been explained by liardecn, Bratlain, and Shockley, many featuresof the transistor are nicely explained by this picture of its action; but, forpresent purposes of circuit analysis, we shall now take the purely empirical EQUIVALENT CIRCUIT Equations. /■lg21 + t2Cg22 + Z^) = 0 Circuit determinant A = C^u + Zg)(^i2 + Zl) — %-^-ii Input impedance Zu = %u — Output impedance Z22 = ^22 — Operating power gain Go = ^RgRl ?22 + Zl ?ii + Zg A 1 (Zg + Zl)% Insertion power gain G\ = Fig. 3—Synopsis of general four-pole—imjiedancc analysis. view and regard the transistor as a black box whose performance is to bedetermined by electrical measurements on its terminals. A picture of a black box is shown in Fig. 3 along with the equations de-scribing it. The performance is completely characterized if one knows thevoltage and current at each of the two pairs of terminals. Now, of thesefour variables, only two are independent since, if any two are fixed, the othertwo are determined. One can therefore describe the network in terms ofany two variables and, since there are six possible ways to choose a pair ofvariables from a set of four, there are sk ways of describing the network. To recall what is done for electron tubes is helpful. In th
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