Let the BJT of Fig. P6.5 have rb 5 300 V, 0 5 100, and fT 5 600 MHz. (a) Assuming C 5 0 and VA 5 `, sketch and label the high-frequency equivalent circuit. Hence, use physical insight to predict the...

Let the BJT of Fig. P6.5 have rb 5 300 V, 0 5 100, and fT 5 600 MHz. (a) Assuming C 5 0 and VA 5 `, sketch and label the high-frequency equivalent circuit. Hence, use physical insight to predict the asymptotic values of Z in the limits f → 0 and f → `. (b) Use the test method to obtain an expression for Z(f), put it in the standard form of Eq. 6A.1, and sketch and label the frequency plot of uZ(jf)u (use logarithmic scales). What are the values of its zero and pole frequencies? (c) Use physical insight to discuss how the above frequency plot will change if C 5 0.5 pF. Hint: the effect of C Þ 0 is to introduce an additional high-frequency pole, thus causing a 21-dec/dec bend in the high-frequency asymptote (refer also to Appendix 6A).