EECE 363 Quiz 4B 2008 Solutions

Answer the following questions suggested time to

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Unformatted text preview: n’ = 0.2 mA/V2, L1 = L2 = 0.8 μm, W1 = 8 μm, and VA=∞. Answer the following questions. (Suggested time to spend: 15 min) (a) Find the values for VGS1 and R1 to establish a current of 0.2 mA in Q1. (3 points) ID1 = (1/2)kn’(W1/L1)(VGS1 − Vt)2 = (1/2)(0.2 mA/V2)(8/0.8)(VGS1 − 0.6V)2 = (1 mA/V2)(VGS1 − 0.6V)2 For ID1 = 0.2 mA, VGS1 = ±[(0.2mA)/(1mA/V2)]1/2 + 0.6V = 1.05 V or 0.15 V VGS1 = 1.05 V for VGS1 > Vt ∴R1 = (3V − VGS1)/ID1 = (3V− 1.05V)/(0.2mA) = 9.75 kΩ (b) With the condition in (a), find the values for R2 and W2 so that the transistor Q2 operates in saturation with a current of 0.5 mA and a drain voltage of 1 V. (3 points) For Q2 to conduct 0.5 mA with VDS2 = 1 V, R2 = (3V − VDS2)/(0.5mA) = (2V)/(0.5mA) = 4 kΩ Since VGS2 = VGS1, ID2 = (W2/W1)ID1 = 0.5 mA, or W2 = [(0.5mA)/(0.2mA)](8μ...
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