12.5.5. I-V Characteristics of p-MOSFET

So, to start with let we go for the basic structure of the p-MOSFET keeping in mind that n-MOSFET in as background information.

So, here the MOSFET for p-MOS type I should say where the channel it is and the channel it is supposed to be p-type and this is the cross sectional view of p-type MOSFET. Just for your reference I am also keeping the n channel MOSFET. So, I should say just for our reference we are keeping n-type MOSFET.

The basic structure of a p-MOSFET involves a p-type channel, which allows holes to flow, in contrast to the n-type channel of an n-MOSFET that allows electrons to flow. The p-type channel is embedded within an n-type substrate. This arrangement is essential for the operation of the p-MOS device, as it relies on the movement of holes as charge carriers.

Think of p-MOSFET like a water pipeline system. In this case, the p-type is the pipe where positive water (holes) flows, similar to how holes flow in the p-MOSFET, while the n-type is a reservoir that controls the flow. You need the right 'pressure' (potential) to allow the water to flow through the system.

Now, here at the gate we like to prefer to apply some voltage. So, that the channel supposed to be getting created and we want to convert this channel from n-type to p-type. So, definitely we required applying ‒ve potential with respect to source as well as body.

As a result it produces a current in the same direction. And, now this current since it is flowing from source to drain just to have proper convention of the +ve current flow, we may call this is I .

For proper operation of a p-MOSFET, a negative gate voltage is applied relative to both the source and body. This negative voltage helps create a p-type channel by attracting holes into the channel, which is crucial for the device's functionality. When the p-MOSFET is activated, current flows from the source to the drain.

Imagine the p-MOSFET gate voltage as a gatekeeper who allows or blocks people (holes) from passing through. By applying a negative voltage, it's like telling the gatekeeper to let people in, allowing the current to flow smoothly from one side to the other.

As a result there will be a current flow and this current it is flowing from source to drain and then it is going to the drain. So, this I it is flowing from source to drain. Now, before we go for this flowing in fact, similar to n-MOS, V it reaches to a value a critical value called threshold. And, if the holes concentration here it is exactly equal to the electron concentration deep into the substrate, then we call that channel portion or the surface of the channel got converted from n-type to p-type.

Current in a p-MOSFET flows from the source to the drain due to the movement of holes. As the gate voltage is increased (becomes more negative), it eventually reaches a threshold value, which leads to sufficient hole concentration, allowing the channel to conduct current effectively. At this point, the channel is said to be inverted.

Think of reaching the threshold voltage like reaching a certain level on a rock climbing wall. Once you reach that critical point (threshold), you have the grip you need (hole concentration) to climb and move up (current flow).

So, we can say that the current equation I depends on the gate-source voltage V and the drain-source voltage V , specifically on how they relate to the threshold voltage. When these relationships are established, we can derive the current equation that shows how the p-MOSFET behaves under varying conditions.

The I-V characteristics of the p-MOSFET are derived based on the voltages applied across its terminals. The current through a p-MOSFET is related to the gate-source voltage, the drain-source voltage, and the threshold voltage. This involves calculating how much effective voltage is contributing to the current based on these factors.

Think of the I-V characteristics as the performance chart of a car. The gate-source voltage would be like the gas pedal pressure, the drain-source voltage like the road incline, and the threshold voltage is the car's minimum speed before it can start moving. By analyzing how these factors interact, we can predict the car's speed on different road conditions (different circuit conditions).

--