Let me share very basic concepts of semiconductor as simple as possible.
Theoretically, semiconductor materials need energy to excite its electrons from valence to conduction band. You can think of valence band as the parking lots by the side of the road. Each cars needs to be activated in order to drive its way to the main road. The main road in this case is the conduction band. The activation energy can be coming from either voltage or heat. That is also the basic of p-n junction.
Now, let's talk about the transistor itself. It is actually a combination of several p-n junction. A MOSFET transistor is analogous to a tap water. It is able to block the water from flowing and able to open the flow. So, in MOSFET, the switch lies in the gate. We apply a voltage to either turn on or off the transistor. If the absolute voltage is greater than the threshold voltage, then the transistor will be on and vice versa. The higher the gate voltage, the higher the drain-source current.
There are two possible states of transistor when gate voltage is higher than threshold voltage. First, drain-source voltage is lower than the delta between gate and threshold voltage. In this case, the transistor is at linear or triode region. The transistor is acting like a resistor. Second, drain-source voltage is greater than the delta between gate and threshold voltage. In this case, the transistor is at saturation or active mode.
That's the basic on how the p-n junction and MOSFET transistor work. Next post we will go a little bit deeper.
Theoretically, semiconductor materials need energy to excite its electrons from valence to conduction band. You can think of valence band as the parking lots by the side of the road. Each cars needs to be activated in order to drive its way to the main road. The main road in this case is the conduction band. The activation energy can be coming from either voltage or heat. That is also the basic of p-n junction.
Now, let's talk about the transistor itself. It is actually a combination of several p-n junction. A MOSFET transistor is analogous to a tap water. It is able to block the water from flowing and able to open the flow. So, in MOSFET, the switch lies in the gate. We apply a voltage to either turn on or off the transistor. If the absolute voltage is greater than the threshold voltage, then the transistor will be on and vice versa. The higher the gate voltage, the higher the drain-source current.
There are two possible states of transistor when gate voltage is higher than threshold voltage. First, drain-source voltage is lower than the delta between gate and threshold voltage. In this case, the transistor is at linear or triode region. The transistor is acting like a resistor. Second, drain-source voltage is greater than the delta between gate and threshold voltage. In this case, the transistor is at saturation or active mode.
That's the basic on how the p-n junction and MOSFET transistor work. Next post we will go a little bit deeper.
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