Textbook › Part I The Physics of Semiconductors
CHAPTER 05
CMOS — Why It Sips Power
Nearly every digital circuit built today is made of CMOS
(complementary MOS). The "complementary" part refers to using nMOS and pMOS transistors in pairs.
The simplest example is the inverter, which flips its input: give it a 1 and it puts out a 0, give it a 0 and it puts out a 1. You build it by stacking a pMOS on top and an nMOS underneath.
- Input is 0 (low voltage)
- The pMOS is ON, the nMOS is OFF. The output is tied to the supply rail, so it reads 1.
- Input is 1 (high voltage)
- The pMOS is OFF, the nMOS is ON. The output is tied to ground, so it reads 0.
The thing to notice is that in neither state is there a path for current to flow from the supply to ground. One of the two is always OFF, so the road is blocked.
Comments
Sign in to comment