34.1.6. Finding Drain Resistance

Try these first

1. 1.

   What is the role of bias resistors in a common source amplifier?

   Hint

   Think about what voltage needs to be applied at the gate.

2. 2.

   Define threshold voltage.

   Hint

   What happens when VGS is below this value?

3. 3.

   What is the approximately calculated value of RD using Vdd = 12V, VGS = 2V, and IDS = 0.5 mA?

   • 11 kΩ
   • 6 kΩ
   • 5 kΩ

   Hint

   Apply the formula for RD.

4. 4.

   True or False: Increasing the bias current will always lead to a higher output swing.

   • True
   • False

   Hint

   Consider how changes in current can affect range.

5. 5.

   Design a common source amplifier for a desired output voltage swing of +/- 3V using Vdd = 12V and a threshold voltage of 1V. Determine the values of R1, R2, and RD.

   Hint

   Break down the design based on maintaining balance around the center voltage.

6. 6.

   What will happen to the output gain if RD is increased without changing VGS? Explain and calculate.

   Hint

   Look into the effects on gain per the transistor’s equations to fully understand this.