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Question: sing the diode of ex 23 in the circuit of...

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sing the diode of Ex. 2.3 in the circuit of Fig. 2.29, estimate the frequency of the mput signal when requency of the on. the AC component of vit is 707 V (i.e., estimate the 3 dB V out 10 k n-well Vin l mV Substrate Figure 2.29 Treating the diode as a capacitor. See Problem 2.7


Chapter 2 The Well 45 The total diode depletion capacitance between the n-well and the p-substrate is the parallel combination of the bottom and sidewall capacitances, or (2.17) nt M 2 Substituting in the numbers, we get 1pF + 0.120 pE 1.120 p 0.33 0.33 0.759 0.739 A sketch of how this capacitance changes with reverse potential is given in Fig. 2.15. Notice that when we discuss the depletion capacitance of a diode, it is usually with regard to a reverse bias (V, is negative). When the diode becomes forward-biased minority carriers, electrons in the p material and holes in the n material, injected across the junction, form a stored or diffusion charge in and around the junction and give rise to a storage or diffusion capacitance. This capacitance is usually much larger than the depletion capacitance. Furthermore, the time it takes to remove this stored charge can be significant Ci, diode depletion capacitance ↑ C,o, zero-bias depletion capacitance 1.12pF Vo, diode voltage o Figure 2.15 Diode depletion capacitance against diode reverse voltage.

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