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Question 12.22: Objective: Determine the pole of the gain stage that include...

Objective: Determine the pole of the gain stage that includes a feedback capacitor.

Consider a gain stage with an amplification A = 10³ , a feedback capacitor C_{F} = 30  pF, and a resistance R_{2} = 5 × 10^{5}  Ω.

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The effective input Miller capacitance is
C_{M} = C_{F} (1 + A) \cong (30)(1000)  pF = 3 × 10^{−8}  F
The dominant-pole frequency is therefore
f_{P1} = \frac{1}{2π  R_{2}  C_{M}} = \frac{1}{2π(5  ×  10^{5})(3  ×  10^{−8})} = 10.6  Hz
Comment: The pole of the second stage can be moved to a significantly lower frequency by using the Miller effect.

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