# A BiCMOS Darlington is shown in Fig. 3.76. The bias voltage V B is adjusted for a dc output voltage of 2 V. Calculate the bias currents in both devices and then calculate the small-signal voltage gain Ï o /Ï i of the circuit. For the MOS transistor, assume W = 10µm, L=1µm, Î¼ n C ox = 200 µA

Chapter 3, Problems #12

A BiCMOS Darlington is shown in Fig. 3.76. The bias voltage V

_{B}is adjusted for a dc output voltage of 2 V. Calculate the bias currents in both devices and then calculate the small-signal voltage gain Ï…_{o}/Ï…_{i}of the circuit. For the MOS transistor, assume W = 10µm, L=1µm, Î¼_{n}C_{ox}= 200 µA / V^{2}, V_{t}= 0.6 V, Î³ = 0.25 V^{1/2}, Ï•_{f}= 0.3 V, and Î» = 0. For the bipolar transistor, assume I_{S}= 10^{ˆ’16}A, Î²_{F }= 100, r_{b}= 0, and V_{A}†’ˆž. Use SPICE to check your result. Then add Î» = 0.05 V^{ˆ’1}, r_{b}= 100, and VA = 20 V and compare the original result to the result with this new transistor data. Finally, use SPICE to compute the dc transfer characteristic of the circuit.**Fig. 3.76:**

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**Related Book For**

## Analysis and Design of Analog Integrated Circuits

5th edition

**Authors:** Paul R. Gray, Paul J. Hurst Stephen H. Lewis, Robert G. Meyer

**ISBN:** 978-0470245996