Example 1

1. Example 1 At t=0 the voltages shown are applied. Determine the steady state voltage for Vx S IC = 0V G 1V D 3V At t=0, is the transistor OFF? • current will flow in the direction indicated charging up the capacitor

2. Steady state will occur when: • Vx is no longer changing • When ID = 0 • Ways for ID = 0: • 1) OFF • ON • Saturation • Linear

3. For our problem: • Saturation, Vgs = VTN • 3) Linear, Vds = 0 1V – Vx = ½ Vx = 1/2 Vx = 3V Vx = ½ happens first. This is the answer. Observation: As Vx (Vs) charges Vgs . The current stops flowing when Vgs = VTN. The condition of Vx=Vs = Vd never happens.

4. Example 2 At t=0 the voltages shown are applied. Determine the steady state voltage for Vx S IC = 1.75V G 2V D 3V At t=0, is the transistor OFF? • No current can flow to charge up the capacitor. The steady state value for Vx is 1.75V

5. Example 3 At t=0 the voltages shown are applied. Determine the steady state voltage for Vx as a function of Vin for Vin: 0 to 3V S IC = 0V G 3V D Vin At t=0, what values for Vx would cause the transistor to be OFF? • current will flow in the direction indicated charging up the capacitor

6. For our problem ID = 0: • Saturation, Vgs = VTN • 3) Linear, Vds = 0 3V – Vx = ½ Vx = 2.5 Vx = Vin Which happens first? Vx = Vin Vx • With these problems Vs=Vd, unless Vgs = VTN happens first, preventing current flow. 2.5 2.5 Vin

7. Example 4 At t=0 the voltages shown are applied. Determine the steady state voltage for Vx D Now the drain IC = 3V G 2V S 1V At t=0, is the transistor OFF? • Current can flow to discharge the capacitor.

8. For our problem: • Saturation, Vgs = VTN • 3) Linear, Vds = 0 3V – 1 = 1/2 cannot happen Vx = 1V Vx = 1V

9. For PMOS transistors Steady state will also occur when: • Vx is no longer changing • When ID = 0 • Ways for ID = 0: • 1) OFF • ON • Saturation • Linear