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The diffusion capacitance in a diode is associated with the storage of minority carriers, which occurs primarily under forward bias. In reverse bias, the depletion region widens, and the majority carriers are pulled away from the junction, minimizing the injection and storage of minority carriers. As a result, the diffusion capacitance becomes negligible because there is insufficient minority carrier recombination and storage in this condition. Thus, the behavior of the diode under reverse bias is dominated by junction capacitance rather than diffusion capacitance.
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Does the diffusion capacitance exit in forward biased diode?
Yes
What is the difference between junction capacitance and diffusion capacitance?
Junction capacitance occurs at the depletion region of a p-n junction diode and is associated with the charge storage due to the electric field created by the built-in potential; it varies with the applied voltage. In contrast, diffusion capacitance is related to the charge carriers' movement across the junction when the diode is forward-biased, and it reflects the transient response of the charge carriers as they diffuse into the depletion region. Essentially, junction capacitance is linked to the static electric field, while diffusion capacitance is dynamic, arising from the flow of charge carriers.
What is the value of the transition capacitance for a silicon diode when VD 0?
The transition capacitance of a silicon diode, often referred to as junction capacitance, depends on the applied voltage across the diode. When the diode is reverse-biased (VD < 0), the transition capacitance is positive and becomes larger as the reverse voltage increases. However, when VD = 0, the transition capacitance is at its minimum value, which can be approximated using the formula (C_j = \frac{\epsilon A}{W}), where (W) is the depletion width, (A) is the junction area, and (\epsilon) is the permittivity of the semiconductor material. At VD = 0, the depletion region is narrow, resulting in a relatively small capacitance.
How is a non-conducting diode biased?
A nonconducting diode is biased in the reversed direction (reverse polarization).
On what part of the curve is a reverse biased diode is normally oprated?
A reverse-biased diode is typically operated in the reverse breakdown region of its current-voltage characteristic curve. In this region, the diode allows a small reverse current to flow, which is generally negligible until a certain breakdown voltage is reached. Beyond this breakdown voltage, the diode can conduct significant current, but in normal applications, it operates below this threshold to prevent damage. Thus, the diode primarily remains in the reverse bias region with minimal current flow.
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 difference between junction capacitance and diffusion capacitance?
Junction capacitance occurs at the depletion region of a p-n junction diode and is associated with the charge storage due to the electric field created by the built-in potential; it varies with the applied voltage. In contrast, diffusion capacitance is related to the charge carriers' movement across the junction when the diode is forward-biased, and it reflects the transient response of the charge carriers as they diffuse into the depletion region. Essentially, junction capacitance is linked to the static electric field, while diffusion capacitance is dynamic, arising from the flow of charge carriers.
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
What is the value of the transition capacitance for a silicon diode when VD 0?
The transition capacitance of a silicon diode, often referred to as junction capacitance, depends on the applied voltage across the diode. When the diode is reverse-biased (VD < 0), the transition capacitance is positive and becomes larger as the reverse voltage increases. However, when VD = 0, the transition capacitance is at its minimum value, which can be approximated using the formula (C_j = \frac{\epsilon A}{W}), where (W) is the depletion width, (A) is the junction area, and (\epsilon) is the permittivity of the semiconductor material. At VD = 0, the depletion region is narrow, resulting in a relatively small capacitance.
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).
On what part of the curve is a reverse biased diode is normally oprated?
A reverse-biased diode is typically operated in the reverse breakdown region of its current-voltage characteristic curve. In this region, the diode allows a small reverse current to flow, which is generally negligible until a certain breakdown voltage is reached. Beyond this breakdown voltage, the diode can conduct significant current, but in normal applications, it operates below this threshold to prevent damage. Thus, the diode primarily remains in the reverse bias region with minimal current flow.
What is the relation between capacitance and forward biased voltage?
q=cv q=dv/dt
