2.5.1. Subthreshold Operation

Try these first

1. 1.

   What is subthreshold conduction?

   Hint

   Think about the conditions for current flow in transistors.

2. 2.

   Why is subthreshold operation useful?

   Hint

   Consider applications that require battery efficiency.

3. 3.

   What happens when the gate-source voltage is below the threshold voltage?

   • No current flows
   • A small current flows
   • The transistor is damaged

   Hint

   Think about what subthreshold conduction means.

4. 4.

   True or False: Subthreshold operation can lead to significant power savings in low-power devices.

   • True
   • False

   Hint

   Consider the applications of subthreshold operation.

5. 5.

   A subthreshold CMOS device operates at a threshold voltage of 0.4 V and the thermal voltage is 26 mV. If the gate-source voltage is set to 0.3 V and I0 is known to be 2 µA, calculate the subthreshold current ID.

   Hint

   Ensure you’re applying the correct voltage values in the exponential equation.

6. 6.

   Evaluate the performance implications of using subthreshold conduction in a wearable device expected to operate for weeks on a small battery.

   Hint

   Think about the balance between performance and power efficiency.