There should be no restrictions on the speed of operationĪs the world is not just stuck to ideal applications, the functioning of MOSFET is even applicable for practical purposes.The resistance in OFF state should be infinite.When the device functions in ON state, the voltage drop value should be null.In the OFF condition, blocking voltage levels should not hold any kind of limitations.In the ON condition, there has to be the current limitation that it carries.When a MOSFET is supposed to function as an ideal switch, it should hold the below properties and those are To consider this functionality, let us have a look at the ideal and practical characteristics of the MOSFET device. Let us now consider the switching characteristics of MOSFETĪ semiconductor too such as MOSFET or Bipolar Junction Transistor is basically functioned as switches in two scenarios one is ON state and the other is OFF state. When the MOSFET devices function in this linear region, they perform amplifier functionality. Linear/Ohmic Region – It is the region where the current across the drain to source terminal enhances with the increment in the voltage across the drain to source path.Due to this, the saturation region is selected when the devices are supposed to perform switching. In this scenario, the device functions as a closed switch where a saturated level of current across the drain to source terminals flows. This happens only once when the voltage across the drain to source terminal increases more than the pinch-off voltage value. Saturation Region – In this region, the devices will have their drain to source current value as constant without considering the enhancement in the voltage across the drain to source.Here, the device functions as a basic switch and is so employed as when they are necessary to operate as electrical switches. Cut-off Region – It is the region where the device will be in the OFF condition and there zero amount of current flow through it.To the most general scenario, the operation of this device happens mainly in three regions and those are as follows: Enhancement Mode N Channel MOSFET Regions of Operation Please refer to this link to know more about – N-Channel MOSFET. Instead of positive voltage if we apply negative voltage then a hole channel will be formed under the oxide layer. Now, if a voltage is applied between the drain and source the current flows freely between the source and drain and the gate voltage controls the electrons in the channel. The positive voltage also attracts electrons from the n+ source and drain regions into the channel. Upon the reach of electrons, the channel is formed. The depletion region is populated by the bound negative charges which are associated with the acceptor atoms. When we apply the positive voltage with repulsive force at the gate terminal then the holes present under the oxide layer are pushed downward into the substrate. The current flow in this type of MOSFET happens because of negatively charged electrons. In this type of Field Effect Transistor, the drain and source are heavily doped n+ region and the substrate or body are of P-type. It is a four-terminal device having the terminals as gate, drain, source, body. The N-Channel MOSFET has an N- channel region located in between the source and drain terminals. Please refer to this link to know more about – P-Channel MOSFET.ĭepletion Mode P Channel P Channel Enhanced Mode N- Channel MOSFET The negative gate voltage also attracts holes from the p+ source and drain region into the channel region. The depletion region populated by the bound positive charges which are associated with the donor atoms. When we apply the negative voltage with repulsive force at the gate terminal, then the electrons present under the oxide layer are pushed downwards into the substrate. The flow of current is in the direction of positively charged holes. The drain and source are heavily doped p+ region and the body or substrate is of n-type. It is a four-terminal device having the terminals as gate, drain, source, and body. The P- channel MOSFET has a P- Channel region located in between the source and drain terminals. Instead of the positive voltage, if we apply a negative voltage, a hole channel will be formed under the oxide layer. Now, if a voltage is applied between the drain and source, the current flows freely between the source and drain and the gate voltage controls the electrons in the channel. When electrons are reached, a channel is developed. The depletion region populated by the bound negative charges which are associated with the acceptor atoms.
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