Tunnel Diode Presentation
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Transcript of Tunnel Diode Presentation
![Page 1: Tunnel Diode Presentation](https://reader033.fdocuments.us/reader033/viewer/2022061204/547f427fb37959a22b8b56bd/html5/thumbnails/1.jpg)
Tunnel DiodeZulhilmi b Ab Rafit A124667
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Introduction A Tunnel Diode is s pn junction that exhibits
negative resistance between two values of forward voltage
voltage is increased the current through it decreases.
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Introduction A pn junction with heavy doping of p type and n
type semiconductor materials results in large no of majority carriers Because this large no of carriers, most are not
used during initial recombination that produces depletion layer
Tunneling effect occurs
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Theory p-n junction with highly doped regions creating
very thin barrier (depletion region)
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Theory In such case, there is a probability that electrons
can tunnel from the conduction band of n-region to the valence band of p-region
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Theory (a) the bottom of the n-side
conduction band overlaps the p-side valence band
(b) with a small forward bias electrons can directly tunnel across the small depletion region from the n-side conduction band into the p side valence band,
(c ) for increased forward voltage the tunnel current ceases as the two bands do not overlap anymore (regular pn junction)
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Operation
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Forward bias Also known as negative resistance As voltage begins to increase, electrons at first
tunnel pass through the very narrow p-n junction barrier
because filled electron states in the conduction band on the n-side become aligned with empty valence band hole states on the p-side of the pn junction.
As voltage increases further these states become more misaligned and the current drops
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Forward Bias Zero bias, no current flow
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Forward Bias Small forward bias, Potential barrier still very high Electron tunnel – tunnel current
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Forward Bias Lager voltage Electron tunnel = Hole create Maximum tunneling current
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Forward Bias Higher voltage #electron decrease at n-reagion start tunneling current decrease
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Forward Bias Higher voltage Tunneling Current = 0 regular diode forward current due to electron –
hole injection increases due to lower potential barrier.
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Forward Bias Higher voltage I-V characteristic similar to a regular p-n diode.
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Reverse Bias electrons in the valence band of the p side tunnel
pass directly towards the empty states present in the conduction band of the n side
creating large tunneling current which increases with the application of reverse voltage.
Similar to zener diode