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As the junction temperature increases, the voltage breakdown point for zener mechanism_________.
Is increased
Is decreased
Remains the same
None
Is decreased
As the junction temperature of a zener diode increases, the breakdown voltage for the zener mechanism decreases. This is because the zener mechanism possesses a negative temperature coefficient of breakdown voltage.
As the junction temperature of a zener diode increases, the breakdown voltage for the zener mechanism decreases. This is because the zener mechanism possesses a negative temperature coefficient of breakdown voltage.
╬ФVZтАЛ=TCтАЛтЛЕVZтАЛтЛЕ╬ФT тАФ change in zener breakdown voltage with temperature
TCтАЛ=VZтАЛ1тАЛdTdVZтАЛтАЛ тАФ temperature coefficient of zener diode
The zener mechanism occurs in heavily doped p-n junctions with a very thin depletion region under high electric field strength (>107┬аV/m). As junction temperature increases, the forbidden energy bandgap (EgтАЛ) of the semiconductor material decreases. This reduces the required electric field strength for valence electrons to quantum-mechanically tunnel directly into the conduction band, causing breakdown to occur at a lower reverse voltage.
Zener breakdown occurs in highly doped diodes with breakdown voltages typically below 5 V to 6 V.
Zener mechanism has a negative temperature coefficient (TCтАЛ<0), meaning breakdown voltage decreases with rising temperature.
Avalanche breakdown occurs in lightly doped diodes (VZтАЛ>6┬аV) and has a positive temperature coefficient (TCтАЛ>0).
Around 5.6 V, both zener and avalanche mechanisms offset each other, resulting in a near-zero temperature coefficient.
Predictable voltage regulation across specific operating current ranges.
Fast response time suitable for voltage reference and transient protection circuits.
Temperature sensitivity requires compensation when high thermal stability is needed.
Limited power dissipation capacity requiring external current-limiting resistors.
DC voltage regulators and reference voltage sources.
Waveform clipping and over-voltage protection circuits.
| Feature | Zener Mechanism | Avalanche Mechanism |
|---|---|---|
Breakdown Voltage (VZтАЛ) | Typically < 5 V - 6 V | Typically > 6 V |
Temperature Coefficient | Negative (VZтАЛ decreases as Temp increases) | Positive (VZтАЛ increases as Temp increases) |
Doping Level | Heavily doped (thin depletion region) | Lightly doped (wide depletion region) |
Primary Cause | Direct quantum tunneling due to high electric field | Impact ionization by thermally generated carriers |
Option A is incorrect because an increase in breakdown voltage with temperature describes the avalanche breakdown mechanism.
Option C is incorrect because breakdown voltage is dependent on junction temperature for both zener and avalanche mechanisms.
Option D is incorrect as option B is the valid technical choice.
B is correct тАФ As junction temperature increases, the breakdown voltage for the zener mechanism decreases due to its negative temperature coefficient.
Remember: Zener breakdown has a Negative temperature coefficient (VZтАЛ<5┬аV), while Avalanche breakdown has a Positive temperature coefficient (VZтАЛ>6┬аV). This is a frequent direct question in GATE/ESE/SSC-JE exams.