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Does the diffusion capacitance exit in forward biased diode?
Yes
How is a non-conducting diode biased?
A nonconducting diode is biased in the reversed direction (reverse polarization).
A varactor diode is operated under reverse biased conditionwhy?
because reverse biased current is constant upto avalanche breakdown.
What is the effect of dielectric on the capacitance of a capacitor?
Any variation of the charge within a p-n diode with an applied voltage variation yields a capacitance wich must be added to the circuit model of a p-n diode. The capacitance associated with the charge variation in the depletion layer is called the junction capacitance, while the capacitance associated with the excess carriers in the quasi-neutral region is called the diffusion capacitance. Both types of capacitances are non-linear so that we will derive the small-signal capacitance in each case. We will find that the junction capacitance dominates for reverse-biased diodes, while the diffusion capacitance dominates in strongly forward-biased diodes. The total capacitance is the sum of both.
Why is the input impedance of a jfet so high?
If you mean JFET, it is because the gate junction is reverse biased.
What is the type of capacitance effect exhibited in P-N junction when it is reverse biased?
1. Transition capacitance 2. Diffusion capacitance 3. Space charge capacitance 4. Drift capacitance
Does the diffusion capacitance exit in forward biased diode?
Yes
What is the difference between diffusion capacitance and transition capacitance?
Transition capacitance : A reverse biased PN-junction has a region of high resistivity (depletion layer) sandwiched in between two regions of relatively low resistivity. The P-N regions act as the plates of a capacitor and the depletion layer acts as the dielectric This is known as the transition capacitance or depletion capacitance. Diffusion capacitance : It is the capacitance due to transport of charge carriers between two terminals of a device like the forward biased PN junction. In a semiconductor device with a current flowing through it (for example, an ongoing transport of charge by diffusion) at a particular moment there is necessarily some charge in the process of transit through the device. If the applied voltage changes to a different value and the current changes to a different value, a different amount of charge will be in transit in the new circumstances. The change in the amount of transiting charge divided by the change in the voltage causing it is the diffusion capacitance. The adjective "diffusion" is used because the original use of this term was for junction http://www.answers.com/topic/diode, where the charge transport was via the diffusion mechanism.
What is the capacitance formed at forward biased?
to find the diffusion capacitance we first find the minority charge "close" the depletion edges Qd and then differentiate it with respect to the voltage applied Vd. Cd =[dQd/dVd]vd=tT{ Id(@Vd)/VT}
What is diffusion capacitance in pn junction?
A capacitor is a device that stores charge. Therefore any device that stores charges( static or dynamic) can be said to have capacitance. When a PN diode is forward biased, a current flows due to the majority charge carriers. At a particular instant there will be charges in motion. This is dynamic charge. The capacitance due to storage of dynamic charge is called the diffusion capacitance. We know that C = Q * V. That is capacitance is directly proportional to charge stored. Since the diode current increases exponentially with the voltage applied across it, the dynamic charge also increases exponentially . Hence the diffusion capacitance increases exponentially with the increasing diode voltage.
When both junction of npn diode reverse biased the the diode in what state?
reverse biased
Why ordinary diodes dont work properly At high frequencies?
Because of stray capacitance. At very high frequencies, the inter-electrode capacitance has a low enough impedance that the diode no longer cuts off when reverse-biased, there is still significant conduction via capacitive coupling. High-frequency diodes are constructed so as to minimize this capacitance.
How is a non-conducting diode biased?
A nonconducting diode is biased in the reversed direction (reverse polarization).
What is the relation between capacitance and forward biased voltage?
q=cv q=dv/dt
A varactor diode is operated under reverse biased conditionwhy?
because reverse biased current is constant upto avalanche breakdown.
Why do we get current in reverse bias?
because semiconductor diodes are not perfect insulators when reverse biased. if you want a diode that is a perfect insulator when reverse biased, use a vacuum tube diode.
Why silicon controlled rectifier doesn't work in reverse biased condition?
Because when reverse biased it behaves like any other rectifier/diode.
