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At higher forward voltages, a junction diode is likely to ________.
break down
become noisy
get saturated
burn out
burn out
At higher forward voltages, the current flowing through a PN junction diode increases exponentially. If the power dissipation exceeds the thermal limit of the device, the semiconductor material undergoes irreversible damage, leading to the diode burning out.
MIL-STD-750 (Test Methods for Semiconductor Devices)
At higher forward voltages, the current flowing through a PN junction diode increases exponentially. If the power dissipation exceeds the thermal limit of the device, the semiconductor material undergoes irreversible damage, leading to the diode burning out.
IDтАЛ=ISтАЛ(e╬╖kTqVFтАЛтАЛтИТ1) тАФ The diode current equation relating current to forward voltage.
PDтАЛ=VFтАЛ├ЧIDтАЛ тАФ Power dissipation formula indicating heat generation.
As the forward voltage VFтАЛ increases, the current IDтАЛ follows the Shockley diode equation: IDтАЛ=ISтАЛ(e╬╖kTqVFтАЛтАЛтИТ1). Excessive current causes high power dissipation defined by PDтАЛ=VFтАЛ├ЧIDтАЛ. When this power exceeds the maximum rated dissipation, the localized heat cannot be dissipated into the surroundings, causing the internal lattice structure to melt or oxidize, resulting in permanent device failure.
Forward conduction involves charge carrier injection across the depletion region.
Thermal runaway occurs when high current leads to excessive heat, lowering the barrier potential and drawing more current.
Diode data sheets specify a 'Maximum Forward Current' and 'Maximum Power Dissipation' to prevent burnout.
Burnout is a physical, irreversible failure mode compared to simple reverse bias breakdown.
Option A is incorrect because 'breakdown' typically refers to the reverse bias Zener or Avalanche effect, which is often non-destructive if current is limited.
Option C is incorrect because 'saturation' refers to reaching the maximum possible current in a transistor (like BJT) or the state where current doesn't increase with voltage, which does not apply to simple PN diodes under excessive load.
Option B is incorrect because while noise (like shot noise) increases with current, the primary catastrophic effect at excessive voltage is thermal failure.
D is correct тАФ At higher forward voltages, excessive current leads to uncontrollable power dissipation and thermal destruction, causing the diode to burn out.
Always remember that PN diodes are current-controlled devices in terms of thermal limit; once the junction temperature exceeds the material's limit (e.g., 150┬░C for Silicon), failure is inevitable.
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