Lambda diode

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Circuit of a lambda diode with two JFETs.
IU characteristic

A lambda diode is an elementary electrical circuit with two connections, which consists of two junction field effect transistors (JFETs) and, similar to a tunnel diode, has a differential negative resistance in its characteristic curve . In the characteristic curve shown here, which shows the current I D through the lambda diode as a function of the applied voltage U D , this is the case in the characteristic curve section marked in red. The name is derived from the shape of the IU characteristic, which roughly resembles the Greek letter λ ( lambda ) .

Areas of application

In contrast to tunnel diodes, whose differential negative resistance is in the range from 70 mV to 350 mV, lambda diodes have a differential negative resistance over the range from 1.5 V to 6 V. As with tunnel diodes, areas of application are primarily in the area of oscillators , where the differential negative resistance is used to generate vibrations. Due to the larger modulation range, they offer circuit advantages over tunnel diodes. However, since it is not a quantum mechanical tunnel effect, they cannot be used as quickly and at such high frequencies as tunnel diodes.

Other areas of application are power-saving digital circuits based on combinations of modified lambda diodes. In this way, like in CMOS technology with metal-oxide-semiconductor field effect transistors (MOSFETs) with JFETs, logic gates such as AND gates , OR gates and non-gates can be implemented. However, since MOSFETs can be integrated into integrated circuits that require less space, JFETs are of little practical importance in this area of ​​application. Furthermore, bistable multivibrators for memory cells can also be implemented by means of lambda diodes.

In addition to the version with one N-channel and one P-channel JFET each, as shown in the figure opposite, lambda diodes can also be implemented as a combination of an N-channel JFET with a PNP bipolar transistor and two resistors .

Individual evidence

  1. ^ G. Kano: The Lambda diode: versatile negative-resistance device , in Electronics , No. 48 (13), 1975, pages 105 to 109
  2. ↑ Digital devices based on complementary junction field effect transistors (PDF; 807 kB)
  3. ↑ U.S. Patent No. 4,376,986: Double Lambda diode memory cell
  4. ↑ Oscillations and Regenerative Amplification using Negative Resistance (PDF; 362 kB)