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Question 6.18: Does cascoding increase the GBW product? Assume that the out...

Does cascoding increase the GBW product? Assume that the output pole is dominant.

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No, it does not. Equation (6.100) suggests that the GBW product is independent of the output resistance. More specifically, if cascoding in Fig. 6.44 raises the output impedance by a factor of K, then |A_0| (= G_m R_{out}) rises and ω_p falls, both by a factor of K, yielding a constant GBW product.

GBW= \frac{g_{m1}}{2πC_L}                                           (6.100)

6.44

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