Wikipedia gives this example of an I-V curve of a tunnel diode. What is the "noise" in the negative resistance region? Is it a characteristic of the diode or of the measuring circuit? The caption says "taken on a Tektronix model 571 curve tracer."

Tunnel Diode I-V curve from Wikipeida



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    \$\begingroup\$ I wouldn't be surprised if it is caused due to the negative dynamic resistance, which is a well known condition to start oscillations. There is very little info available though from just the single plot, not even the type of the equipment nor its settings. I'm curious what "mechanism" is used the measure such a curve. \$\endgroup\$ – jippie Apr 21 '15 at 20:37
  • \$\begingroup\$ A link to the source of the picture isn't just useful; your whole question relies on it. \$\endgroup\$ – Andy aka Apr 21 '15 at 21:14

The Tektronix 571 Curve Tracer used in the photograph is an early instrument whose Operators Manual is here http://w140.com/tek_571.pdf. The manual does not mention tunnel diodes but states on p.2-9 that images of transistor behaviour at very low voltages and current may be noisy. It also acknowledges on p.3-18 a problem with devices that oscillate. It is not capable of reducing noise by integrating repeated measurements. I speculate that dwelling at any point on the negative resistance region for the time required to measure each sample creates a high gain amplifier for ambient noise, or even an oscillation at a frequency far higher than the ADC is able to "see"

  • \$\begingroup\$ Nice, I assume it would be easy to do a voltage sweep of a tunnel diode and get a decent sweep of the measured current. \$\endgroup\$ – George Herold Apr 22 '15 at 0:54

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