5.2.1. Threshold Voltage (VthV_{th}) Variation

Try these first

1. 1.

   What does Vth stand for?

   Hint

   Think about what voltage makes a transistor switch on.

2. 2.

   Name one source of Vth variation.

   Hint

   Consider what might change during the fabrication process.

3. 3.

   What is the effect of increased doping concentration on Vth?

   • Increases Vth
   • Decreases Vth
   • No effect

   Hint

   Think about what happens when a material gets 'more crowded' with impurities.

4. 4.

   True or False: Thicker gate oxide decreases control over the channel.

   • True
   • False

   Hint

   Consider how the gate needs to effectively influence the channel for the transistor to switch.

5. 5.

   Suppose a CMOS circuit has an average Vth of 0.5V. If doping concentration increases by 20%, predict the new Vth and discuss the implications for the circuit's performance.

   Hint

   Use the relationship between doping and Vth to inform your prediction.

6. 6.

   Design a simple circuit that incorporates redundancy to combat Vth variation and explain how it would mitigate performance losses.

   Hint

   Consider how having backups in a system can improve reliability.