# Understanding a circuit containing PMOS and NMOS

I have the following circuit, the top is a PMOSFET, bottom is NMOSFET

I'm having troubles understanding what exactly is happening here. I've dealt with PMOSFETs and NMOSFETs separately, and here combined, it seems as though I have no idea as to how to approach this.

Let's say I ground $V_{\text{in}}$ (=0), then is the difference in voltage from $V_{\text{in}}$ to the top of the PMOS 2.5V? and vice versa with the NMOS? How does that affect $V_{\text{out}}$ and the rest of the currents running through the circuit?

I'm not looking for answers, but rather, a way to understand what goes on here.

• It sounds like you actually haven't internalized the very basic idea of potential difference. Yes, if one node is at 0 V (relative to "ground") and another is at 2.5 V, the difference between them is 2.5 V. Commented Mar 6, 2017 at 18:57
• When I say "basic" I mean it's important to understand this in order to understand just about everything else in EE, not "you're dumb if you don't understand it". Commented Mar 6, 2017 at 19:06
• Look at it separately. Because what activates one, dactivates the other. It is an invertor. Commented Mar 6, 2017 at 19:48
• Wow. This looks like a NOT gate ;)
– user103380
Commented Mar 6, 2017 at 20:07
• It not a NOT gate because the gnd is not at 0V but at -2.5 V ! Commented Mar 6, 2017 at 22:48

To understand what is happening it is better not to apply a static voltage to $V_{\text{in}}$ but instead a Sinus
Think about what is happening while the Voltage is rising from 0V to peak (The n-Mosfet is "opening" as the voltage is rising and so your $V_{\text{out}}$ is getting more "Negative)