Negative resistance

About: Negative resistance is a research topic. Over the lifetime, 2335 publications have been published within this topic receiving 22341 citations.

Some basic characteristics of broadband negative resistance oscillator circuits

Abstract: This paper discusses the behavior of oscillators with multiple-resonant circuits. It discusses the condition for free-running stable oscillations, the injection locking phenomena, the stable locking range, the noise of free-running and injection-locked oscillators, and a condition for parasitic oscillations in detail, and presents a graphical interpretation of this study for clarity. Finally, this paper shows how broadbanding of oscillators can be achieved with a double-resonant circuit. This provides a systematic guide for the design of broadband frequency deviators and broadband injection-locked oscillators for numerous applications.

Signal and Noise Properties of Gallium Arsenide Microwave Field-Effect-Transistors

Abstract: Publisher Summary This chapter examines the signal and noise properties of gallium arsenide (GaAs) microwave field-effect transistors (FET) High frequency gallium arsenide field-effect transistors (GaAs FETs) have demonstrated remarkably low noise figures and high power gains at microwave frequencies A practical microwave GaAs FET is usually fabricated by deposition or diffusion of source, gate, and drain contacts on the surface of an appropriately doped thin epitaxial n-type layer This layer, in turn, is grown on a semi-insulating wafer by either a vapor or liquid epitaxial technique The apparent minor role played by the negative resistance region in practical short-gate FETs suggests that radiofrequency instabilities due to this region, if they exist, occur at frequencies far above the normal frequency regime of microwave FETs The small-signal equivalent circuit of the FET, valid up to moderately high frequencies is elaborated It is found that noise in a microwave GaAs FET is produced both by sources intrinsic to the device and by thermal sources associated with the parasitic resistances

Self-consistent study of the resonant-tunneling diode

Abstract: Quantum transport in the resonant-tunneling diode (RTD) is modeled here with the Wigner formalism including self-consistent potentials for the first time. We examine the computational aspects of the Wigner-function approach and the boundary conditions for the model. The calculated I-V characteristics show an intrinsic bistability in the negative-differential-conductivity region of the curve. Intrinsic bistability results from charge storage and the subsequent shifting of the internal potential of the device. The cathode region of the RTD shows a strong depletion and quantization of electrons in a deep triangular potential well, which reduces the barrier height to a ballistic electron injected from the cathode, enhancing the valley current and reducing the peak-to-valley ratio. Undoped spacer layers prevent the formation of a deep quantum well at the cathode barrier, and the distribution does not deplete as sharply as without the spacer layer. The I-V curve with the spacer layers shows a much lower negative resistance, and a sharper bistable region. A finite relaxation time for the electrons increases the negative resistance, reduces the peak-to-valley ratio of the current, and causes a ``soft'' hysteresis in the bistable region. A zero-bias anomaly is found to result from high-momentum tails in the distribution at the barrier interface. These high-momentum tails contribute a small high-conductance current. The transient current during switching from the peak to the valley of the I-V curve shows inductive behavior and negative resistance for frequencies below 2 THz.

Quantum well oscillators

Abstract: Oscillations have been observed for the first time from double barrier resonant tunneling structures. By eliminating impurities from the wells, we have been able to increase the tunneling current density by a factor of nearly 100. With the attendant increase in gain and improved impedance match to the resonant circuit, the devices oscillated readily in the negative resistance region. Oscillator output power of 5 μW and frequencies up to 18 GHz have been achieved with a dc to rf efficiency of 2.4% at temperatures as high as 200 K. It is shown that higher frequencies and higher powers can be expected.