Common-Collector and Common-Base Amplifiers Figure 9-22 shows CC and CB amplifiers and their hybrid equivalent circuits. the

general gain and impedance equations we derived in Section 9-3 are app 9 these configurations, with the usual modifications to reflect the presence of ext bias resistors.T in the common-collector amplifier .shown in Figure 9-23 has the following” parameters: h; = 1400 = 1 = -X to-S (silage).I logistic the characteristically large value for the input resistance of an emitter foil lower. 2. = COO kU) 1/ (150 kO) II fill = 32.9 kO 3. From equation 9-15.It is important to include minus signs in all computations involving negative quantities. Notice. for example, that is a negative quantity. Failure to use the proper neuralgic signs will lead to radically incorrect solutions. This precaution is equally important in the next counterexample the is in a common-base configuration, so we must use CB h parameters to analyze it. Since only two of the given parameters Me CB parameters, we must use the conversion equations in Table 9-2 and the CE parameter values that are given \0 find and hob: ‘.

**CC and CB ****Approx**

the computations shown in the preceding two examples suggest some approximations that .:an be used in the analysis of most practical CC and CB amplifiers. The c< union-collector input impedance is, to a ,dose approximation, (Using (9-47) In Example 9-10 gives rift = 72.72 kn, in comparison to the calculated value of 72.82 kU. A good approximation for the common-collector voltage gain is Using (9-48) in Example 9-10 gives A. = 0.981, the same result (to 3 decimal places) calculated there. It is usually the case that hit in which case (9-48) reduces to the assumption for an emitter follower. Since h.and his very small, the output impedance of a CC amplifier can be approximated;’ y Using this approximation in Example 9-10 gives 23.65 n, in comparison with the calculated value of 23.7 n. The current gain of a CC amplifier is, from equation 9-18,Using this approximation in Example 9-’11 gives hr, 12 n, in comparison to the calculated value or 12.24 n. The voltage gain of a CB .Implementer is approximated by summation, that h”,L and HRH/are both negligibly small. As seen in E Ie 9-11, these quantities had values 0.002 and -0.25, respectively. Under that consumption,the computations shown in the preceding two examples suggest some approximations that .:an be used in the analysis of most practical CC and CB amplifiers. The c< union-collector input impedance is, to a ,dose approximation, (Using (9-47) In Example 9-10 gives rift = 72.72 kn, in comparison to the calculated value of 72.82 kU. A good approximation for the common-collector voltage gain is Using (9-48) in Example 9-10 gives A. = 0.981, the same result (to 3 decimal places) calculated there. It is usually the case that hit in which case (9-48) reduces to the assumption for an emitter follower. Since h.and his very small, the output impedance of a CC amplifier can be approximated;’ y Using this approximation in Example 9-10 gives 23.65 n, in comparison with the calculated value of 23.7 n. The current gain of a CC amplifier is, from equation 9-18,Using this approximation in Example 9-’11 gives hr, 12 n, in comparison to the calculated value or 12.24 n. The voltage gain of a CB .Implementer is approximated by summation, that h”,L and HRH/are both negligibly small. As seen in E Ie 9-11, these quantities had values 0.002 and -0.25, respectively. Under that consumption,