- Lambda diode
. The term refers to the shape of the V/I curve of the device, which resembles the Greek letter λ "(lambda)".
Lambda diodes work at higher voltage than tunnel diodes. Whereas a typical tunnel diode [ [http://www.datasheetarchive.com/pdf/84703.pdf 1N3712 data sheet] ] may exhibit negative differential resistance between some 70mV - 350 mV, this region occurs between about 1.5V - 6V in a lambda diode due to the higher pinch-off voltages of typical JFET devices. A lambda diode can therefore not replace a tunnel diode directly.
Moreover, in a tunnel diode the current reaches a minimum of some 20% of the peak current before rising again towards higher voltages. The lambda diode current approaches zero as voltage increases, before rising quickly again at a voltage high enough to cause gate-source zener breakdown in the FETs.
It is also possible to construct a device similar to a lambda diode by combining an n-channel
JFET with a PNP bipolar transistor [ [http://www.zen22142.zen.co.uk/Theory/neg_resistance/negres.htm Oscillations and Regenerative Amplification using Negative Resistance ] ] .Applications
Like the tunnel diode, the negative resistance aspect of the lambda diode lends itself naturally to application in oscillator circuits [ [http://users.tpg.com.au/users/ldbutler/NegResDipMeter.htm "A Dip Meter Using the Lambda Negative Resistance Circuit."] Lloyd Butler, "Amateur Radio", January 1997.] and amplifiers. In addition,
bistable circuits such as memory cells have been described [ United States Patent 4376986: Double Lambda diode memory cell; http://www.wipo.int/pctdb/images4/PCT-PAGES/1983/091983/83001335/83001335.pdf] .References
* Rudolf F. Graf, Modern Dictionary of Electronics, 7th ed. P.411. Boston [etc.] : Newnes Press, 1999. ISBN 0-7506-9866-7
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