# A BiCMOS Darlington is shown in Fig. 3.76. The bias voltage V B is adjusted for a

## Question:

_{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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## Step by Step Answer:

**Related Book For**

## Analysis and Design of Analog Integrated Circuits

**ISBN:** 978-0470245996

5th edition

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