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Abdullah Khan(2011-EE-578) Danyyal Aziz(2011-EE-575) Syed Haider Abbas(2011-EE-572) Mohammad Ali(2011-EE-577) Mateen Ahm

Group Members. Abdullah Khan(2011-EE-578) Danyyal Aziz(2011-EE-575) Syed Haider Abbas(2011-EE-572) Mohammad Ali(2011-EE-577) Mateen Ahmad Rasheed(2011-EE-573) Zeshan Afzal(2011-EE-574) Ans saljook(2010-EE-576). Topic:. Tunnel Diode. Tunnel Diodes (Esaki Diode).

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Abdullah Khan(2011-EE-578) Danyyal Aziz(2011-EE-575) Syed Haider Abbas(2011-EE-572) Mohammad Ali(2011-EE-577) Mateen Ahm

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  1. Group Members • Abdullah Khan(2011-EE-578) • Danyyal Aziz(2011-EE-575) • Syed Haider Abbas(2011-EE-572) • Mohammad Ali(2011-EE-577) • Mateen Ahmad Rasheed(2011-EE-573) • Zeshan Afzal(2011-EE-574) • Ans saljook(2010-EE-576)

  2. Topic: Tunnel Diode

  3. Tunnel Diodes (Esaki Diode) Tunnel diode is the p-n junction device that exhibits negative resistance. That means when the voltage is increased the current through it decreases. Esaki diodes was named after Leo Esaki, who in 1973 received the Nobel Prize in Physics for discovering the electron tunneling effect used in these diodes. Esaki reported the first paper on tunnel diodes in Physical Review in 1958 Tunnel Diode Regular p-n Diode

  4. Contents • Introduction • Definition • Concept of Tunneling? • Circuit Symbol • Negative Resistance Device • Operations • Tunnel Diode As an Oscillator • Other Applications • Advantages • Longevity

  5. Introduction •Tunnel diode is a Heavily-doped p-n junction Impurity concentration is 1 part in 10^3 as compared to 1 part in 10^8 in p-n junction diode •Width of the depletion layer is very small (about 100 A). •It is generally made up of Ge and GaAs.•It shows tunneling phenomenon.

  6. Definition A tunnel diode is a type of semiconductor diode which is capable of very fast operation, well into the microwave frequency region, by using quantum mechanical effects……

  7. Concept of electron tunneling

  8. Circuit Symbol:

  9. Forward Bias Operation Under normal forward bias operation, as voltage begins to increase, electrons at first tunnel 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 p-n junction. As voltage increases further these states become more misaligned and the current drops – this is called negative resistance because current decreases with increasing voltage. As voltage increases yet further, the diode begins to operate as a normal diode, where electrons travel by conduction across the p–n junction, and no longer by tunneling through the p–n junction barrier. Thus the most important operating region for a tunnel diode is the negative resistance region

  10. Reverse Bias Operation When used in the reverse direction they are called back diodes and can act as fast rectifiers. Under reverse bias filled states on the p-side become increasingly aligned with empty states on the n-side and electrons now tunnel through the pn- junction barrier in reverse direction

  11. Tunnel Diode Oscillator An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. They are widely used in many electronic devices. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters, clock signals that regulate computers and quartz clocks, and the sounds produced by electronic beepers and video games.

  12. Tunnel diode as osillator The main object of using tunnel diode is as an oscillotor,the tunnel diode oscillato r is use to convert DC into AC . •First of all when voltage is applied to the circuit the DC voltage source starts charging C1 through R1. •The signal generated by the LC tank circuit is provided by the aditional current by the capacitor through the tunnel diode at its positive peak. •The sustained sine wave is generated at the out put of the circuit.

  13. Other applications •Used in high speed switching circuit.•Used as pulse generator.•Used for storage of binary information. •Sensor modulator for telemetry of temperature in human beings and animals. •Used in electron tunneling microscope. •It is used in amplifier.

  14. Advantages Of Tunnel Diode •Relatively resistant to nuclear radiation.•Useful for high speed operation.•Useful for high frequency operation.•Low power is consumed.

  15. Longevity Esaki diodes are notable for their longevity; devices made in the 1960s still function. Writing in Nature, Esaki and coauthors state that semiconductor devices in general are extremely stable, and suggest that their shelf life should be "infinite" if kept at room temperature. They go on to report that a small-scale test of 50-year-old devices revealed a "gratifying confirmation of the diode's longevity".

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