Semiconductor Oddities - Negative Resistance

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Semiconductors can be used, connected or combined in unusual ways to produce different characteristics or modes of operation or can even be made DIY using unusual materials. I have experimented with transistor simulations of the Lambda diode (negative resistance) and other compound-connected devices, and have collected considerable information on this topic, My hope is that this page, as updated, will unified some information on this topic.

A compound connection of one sort or another is the key to using bipolar and FET transistors in various combinations to simulate other semiconductors and to produce other devices or unusual effects. Lambda diode, Darlington, Sziklai, negative resistance, tunnel diode, unijunction transistor, etc. are some of the words often associated with the results of these compound connections. The use of a bipolar transistor with shorted or open connections to produce a diode with unique characteristics is another way of using transistors. Perhaps the strangest of all is the use of the galvanic couplings of materials, not generally considered as semiconductor materials, to make semiconductors. 

Diodes:

Wideband RF noise generator - a diode and 4 parts

Wideband RF noise generator - a transistor junction and 5 parts

A Crystal Diode Noise Generator - W5TEV


Superdiodes:

More coming here - check back.


Compound connections - Darlington, Sziklai and Cascode:

Wikipedia on Darlington compound connection

Wikipedia on Sziklai compound connection

Wikipedia on the Cascode connection

Darlington-Sziklai Tutorial

Sziklai vs. Darlington

Darlington & Sziklai pairs

Sziklai connection

Darlington connection


Tunnel Diodes, Lamba diodes & Negative resistance:

Tunnel Diodes - K8TSQ

Lost in a Tunnel - K5JKX

Wikipedia on the Lambda diode

Negative Resistance Revived - VK5BR

A Dip Meter Using the Lambda Negative Resistance Circuit - VK5BR

More on negtive resistance including a regenerative receiver - Ramon Vargas-Patron


Unijunction Transistors - UJTs

The Unijunction Transistor - VK3ZRY


DIY semiconductors:

Make semiconductors with unusual materials and put them to work - a fascinating site 


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