The circuit is very small and therefore it is cheap to implement. Accuracy however is poor for the following reasons:
depend on matching of NMOS and PMOS transistors
- PMOS and NMOS transistors have different bulks. So they don't match
- hole and electron mobility differ.
- Thresholds depend on supply voltage VDD
=> spread of trip points usually is in the range of +-25% of VDD
Advantages of the circuit:
- no current consumption if Vin<Vthnmos or Vin>VDD-Vthpmos
Suggested applications: wafe
shaping, simple noise rejection circuits (requires stable VDD).