cutoff
reverse biased
Transistor will be in OFF mode.
When p-n junction of a diode reversed biased then majority carriers are not able to cross the junction and are attracted in respective regions.So current becomes approximately zero.But because of minority carriers a reverse current keeps flowing.It is called Reverse Saturation Current.And due to attraction towards sides,charges go away from junction.So width of depletion reason increases.
Transistor will be in OFF mode.
Transistor will be in OFF mode.
When both junctions of an NPN transistor are reverse biased, the transistor is in the cutoff mode. In this mode, the transistor is effectively turned off, and it does not conduct current between the collector and emitter. As a result, the transistor behaves like an open switch, preventing current flow in the circuit.
The transistor has three regions, emitter,base and collector. The base is much thinner than the emitter while the collector is wider than both. However for the sake of convenience the emitter and collector are usually shown to be of equal size. The transistor has two pn junctions that means it is like two diodes. The junction between emitter and base may be called emitter-base diode or simply the emitter diode.The junction between base and collector may be called collector-base diode or simply collector diode. The emitter diode is always forward biased and the collector diode is always reverse biased.
The diode is neither shorted nor open. It is a zener diode and it is conducting in both directions. If it were truly shorted, it would read closer to zero ohms in both directions.
In the context of a bipolar junction transistor (BJT), the saturation region refers to the state where both the base-emitter and base-collector junctions are forward-biased, allowing maximum current to flow from collector to emitter. The active region occurs when the base-emitter junction is forward-biased while the base-collector junction is reverse-biased, enabling the transistor to amplify signals. The cutoff region is when both junctions are reverse-biased, resulting in minimal current flow, effectively turning the transistor off. These regions define the operational modes of the transistor in electronic circuits.
reverse saturation current is produced by the thermal activity of the diode materials. This current: 1- Is temprature dependant; that is, it increases as temprature. 2- Accounts fot the major portion of diode reverse current surface leakage current is produced by contamination on the surface of the device, allowing current flow to bypass the junction
piv:the maximum value of reverse voltage across a diode that occurs at the peak of the input cycle when the diode is reversed-biased.
if the diode is forward biasedwell practically the current flows in a circuit if and only if an effective resistance is present in the circuit, if we consider the diode to be ideal (barrier potential but no internal resistance) in this case an external resistance is required if we use the approximate model (both barrier potential and internal resistance are considered) we need not use an external resistance the internal resistance itself acts as the effective resistance.if the diode is reverse biased:-the same explanation applies even if the diode is reverse biased but one must take care that the reverse voltage drop on diode should not increase the peak inverse voltage mark the diode would be burnt or damaged if this phenomena occurs.So this can be prevented by adding suitable resistance to the circuit through which the voltage drop on diode can be managed