A lambda diode is an electronic circuit that combines a complementary pair of junction gated field effect transistors into a two-terminal device that exhibits an area of differential

negative resistance In electronics, negative resistance (NR) is a property of some electrical circuits and devices in which an increase in voltage across the device's terminals results in a decrease in electric current through it. This is in contrast to an ordina ...

much like a

tunnel diode A tunnel diode or Esaki diode is a type of semiconductor diode that has effectively " negative resistance" due to the quantum mechanical effect called tunneling. It was invented in August 1957 by Leo Esaki, Yuriko Kurose, and Takashi Suz ...

. 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 may exhibit negative differential resistance approximately between 70 mV and 350 mV, this region occurs approximately between 1.5 V and 6 V in a lambda diode due to the higher pinch-off voltages of typical JFET devices. A lambda diode therefore cannot replace a

directly. Moreover, in a tunnel diode the current reaches a minimum of about 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 electronics, the Zener effect (employed most notably in the appropriately named Zener diode) is a type of electrical breakdown, discovered by Clarence Melvin Zener. It occurs in a reverse biased p-n diode when the electric field enables tunn ...

in the FETs. It is also possible to construct a device similar to a lambda diode by combining an n-channel

JFET The junction-gate field-effect transistor (JFET) is one of the simplest types of field-effect transistor. JFETs are three-terminal semiconductor devices that can be used as electronically controlled switches or resistors, or to build amplifier ...

with a PNP bipolar transistor. A suggested modulatable variant but is a bit more difficult to build uses a PNP based optocoupler and can be tweaked by using its IR diode. This has the advantage that its properties can be fine tuned with a simple bias driver and used for high sensitivity radio applications, sometimes a modified open can PNP transistor with IR LED can be used instead.

Applications

Like the tunnel diode, the negative resistance aspect of the lambda diode lends itself naturally to application in oscillator circuits 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

Literature

* Analog circuits {{electronics-stub