# NMOS and PMOS current sources

I'm really confused with the representation of PMOS device shown in the figure. Since conventional current direction in PMOS is from source to drain, shouldn't the current source be pointing upwards(from node Y to VDD)?

• source is connected to VDD for PMOS – Umar Jul 8 '15 at 8:13

## 1 Answer

Simplest way to remember current direction is by the little arrow indicator on the transistor, for NMOS it is pointing out of the drain thus current flows from source to drain. And for PMOS the arrow is into the source, so flows from source to drain. It is important to remember that the source is indicated by the arrow location. So in the case drawn, NMOS source is on the bottom and PMOS source is on the top.

• Your first sentence is wrong (both in location of arrow and direction of current flow), but you seem to have gotten the description right later. For those not familiar with the subtleties of the symbol differences, it is important to note that you can be deceived by looking at the direction of the arrows on the symbols. See MOSFET symbol - what is the correct symbol. – Tut Jul 8 '15 at 10:20