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The quantum tunneling effect causes a tunnel diode to act much like a fixed resistor of about five or six ohms when reverse-biased or below about 50 millivolts when forward-biased. Between about 50 millivolts and 300 millivolts (0.05 and 0.3 volts), assuming a germanium diode, the impedance of the tunnel diode increases exponentially as the voltage increases. This causes the current to decrease linearly as the voltage increases; the reverse of a fixed resistor. This is called the negative resistance region. Above 300 millivolts, the germanium tunnel diode acts like a regular germanium diode.
The negative resistance region, along with the tunnel diode's low capacitance, can be exploited to create microwave-frequency oscillators. The tunnel diode acts like a voltage-sensitive variable resistor that provides a current inverse to the voltage of a ringing tank circuit. This current is, thus, fed into the tank circuit at the correct phase to compensate for the damping as energy is dissipated by the circuit's resistance.
The "little green man" model used in this video is similar to the LGM model I use to explain the zener diode in the following video: • Zener Diodes
Негізгі бет Tunnel Diodes - Solid-state Devices and Analog Circuits - Day 3, Part 3
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