EECE 363 Quiz 4B 2008 Solutions

5 mav2 vt 1 v and va all l the capacitors in the

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Unformatted text preview: ⏐VGS⏐− ⏐Vt⏐= 4 V) VD = 5V − ⏐VDS⏐= 3 V ID = VD/(1.6 kΩ) = (3 V)/(1.6 kΩ) = 1.875 mA -4- 4) This problem deals with the amplifier below, where the enhancement-type NMOS transistor ⎛W ⎞ is characterized by the following parameters: k n ' ⎜ ⎟ = 0.5 mA/V2, Vt = 1 V, and VA=∞. All ⎝L⎠ the capacitors in the circuit are very large. Answer the following questions. (Suggested time to spend: 25 min) (a) Quantitatively justify that the NMOS is operating in saturation. (3 points) Kn = (1/2)kn’(W/L) = 0.25 mA/V2 Assume saturation: VGS = ±(ID/Kn)1/2 +Vt = ±[(1mA)/(0.25mA/V2)]1/2 + 1V = ±2V + 1V = 3 V or −1 V VGS = 3V for VGS > Vt VD = 5V − IDRD = 5V − (1mA)(5kΩ) = 0 V VS = VG − VGS = 0V − 3V = −3V Then VDS (= 3V) > VGS − Vt (= 3V − 1V...
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