DCBias-MOSFET

DCBias-MOSFET - D =5K, R S = 1K, V G =5, and V DD =15. V T...

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How to approach DC bias MOSFET problem solving: 1. If not obvious, assume transistor is saturated. (80% of the time it is.) 2. Compute V G – Remember I G =0. 3. Write a loop equation thru source. 4. Solve the quadratic equation. 5. Check for V GS that is logically the correct answer. 6. If saturation is confirmed, calculate the unknown and stop. 7. If not, rework using the ohmic region (triode) equation. Example. Given: N channel MOSFET with R
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Unformatted text preview: D =5K, R S = 1K, V G =5, and V DD =15. V T =1 and C(w/L) =0.5 mA/V 2 Find the drain current and source and drain voltages. Solution: V S = I D * R S => Where I D = 0.5K (V GS- V T ) 2 if saturated. Also remember that V GS = V G- V S V S = 10.5 or 1.5 are the solutions to the quadratic equation. Only 1.5 is the logical solution. I D = 0.25(5-1.5-1) 2 = 1.56mA Thus: VD = 15 5K*1.56mA = 7.2 volts....
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