Estimate the series base resistance, series collector resistance r_c, base-emitter capacitance, base-collector capacitance, and collector-substrate capacitance of the high-current npn transistor structure shown in Fig. 2.73. This structure is typical of those used as the output transistor in operational amplifiers that must supply up to about 20 mA. Assume a doping profile as shown in Fig. 2.17.

Shown in figure 2.73

Shown in figure 2-17

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> Buried layer > Emitter Distance, / → Contact opening » Isolation Base > Metal 160 150E 140 130 120E 110E 100- 90 80 70 60 50 30 шI 20 10 nt In Bo n* Impurity concentration, cm-3 (cross section A-A') 1021 Emitter 1020 diffusion (Np) 1019 (Np) Buried layer 1018 Substrate background concentration (NA) 1017 Base (NA) diffusion 1016 1015 2.5 3 57 9/ 10 Epitaxial layer background concentration 15 20 1014 1013 (Np) x Kum)