tunnel diode circuits

Posted on Feb 5, 2014

Leo Esaki invented the tunnel diode in 1957 while working at Sony (Tokyo Tsushin Kogyo at the time). Tunnel diodes have a very narrow, heavily doped p n junction only around 10nm (100 G…) wide that exhibits a broken bandgap, where conduction band electrons and therefore on the n-side are approximately aligned with valence band holes on the p-side facilitate the quantum mechanical tunneling process after which the diode is named.

tunnel diode circuits
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A negative differential resistance in part of their operating range makes them useful for high frequency oscillators. This article in a 1960 edition of Popular Electronics introduces the device`s characteristics and potential uses. By now, just about everyone has heard of the tunnel diode, latest "miracle" from the semiconductor industry. Though related to the tube and transistor, the tunnel diode ordinarily has only two terminals. Yet it differs from other two-terminal devices (resistors, capacitors, and so on) in a very special way. Apply voltage to a resistor, for example, and you can determine current flow by Ohm`s law. Increase the voltage across the resistor, and the current flow through the resistor will increase in proportion. But this is not so with the tunnel diode. The effect which brought about the practical construction of this unique semiconductor was discovered by Dr. Leo Esaki, a brilliant Japanese scientist. Dr. Esaki determined that unusual doping of the germanium-diode junction would cause the current flow to decrease, even though the applied voltage was increased. This effect, known as negative resistance, enables the tunnel diode to perform its unusual feats. Fig. 2. Tunnel-diode forward characteristic curve. In negative-resistance slope range, current through diode decreases even though voltage across diode increases. Figure 1(A) shows a tetrode vacuum tube with a fixed screen voltage of 200 volts and...

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