Series-connection of resonant-tunneling diodes (RTDs) has been considered to be efficient in upgrading the output power when it is introduced to oscillator architecture. This work is for clarifying the same architecture also contributes to increasing oscillation frequency because the device parasitic capacitance is reduced M times for M series-connected RTD oscillator. Although this mechanism is expected to be universal, we restrict the discussion to the recently proposed multiphase oscillator utilizing an RTD oscillator lattice loop. After explaining the operation principle, we evaluate how the oscillation frequency depends on the number of series-connected RTDs through full-wave calculations. In addition, the essential dynamics were validated experimentally in breadboarded multiphase oscillators using Esaki diodes in place of RTDs.

A scheme is proposed for generation of large-amplitude short pulses using a transmission line with regularly spaced series-connected tunnel diodes (TDs). In the case where the loaded TD is unique, it is established that the leading edge of the inputted pulse moves slower than the trailing edge, when the pulse amplitude exceeds the peak voltage of the loaded TD; therefore, the pulse width is autonomously reduced through propagation in the line. In this study, we find that this property is true even when the several series-connected TDs are loaded periodically. By these mechanisms, the TD line succeeds in generating large and short pulses. Herein, we clarify the design criteria of the TD line, together with both numerical and experimental validation.

The transition dynamics of a multistable tunnel-diode oscillator is characterized for modulating amplitude of outputted oscillatory signal. The base oscillator possesses fixed-point and limit-cycle stable points for a unique bias voltage. Switching these two stable points by external signal can render an efficient method for modulation of output amplitude. The time required for state transition is expected to be dominated by the aftereffect of the limiting point. However, it is found that its influence decreases exponentially with respect to the amplitude of external signal. Herein, we first describe numerically the pulse generation scheme with the transition dynamics of the oscillator and then validate it with several time-domain measurements using a test circuit.

A one-dimensional lattice of tunnel-diode oscillators is investigated for potential high-speed frequency divider. In the evolution of the investigated lattice, the high-frequency oscillation dominates over the low-frequency oscillation. When a base oscillator is connected at the end, and generates oscillatory signals with a frequency higher than that of the synchronous lattice oscillation, the oscillator output begins to move in the lattice. This one-way property guarantees that the oscillation dynamics of the lattice have only slight influence on the oscillator motion. Moreover, counter-moving pulses in the lattice exhibit pair annihilation through head-on collisions. These lattice properties enable an efficient frequency division method. Herein, the operating principles of the frequency divider are described, along with a numerical validation.

Ultrahigh-speed compact flash analog-to-digital converters (ADCs) using resonant-tunneling diodes (RTDs) have been designed to demonstrate a high potential of RTD circuits. Novel multi-input subtraction gates are introduced to the encoder to obtain a compact circuit configuration. By assuming 0.1-µm InP-based RTD/HEMT technology, circuit simulations of 4-bit 10-GHz flash ADCs are carried out. It is found that the device counts of the ADC with an 8-input gate are one third that of the ADC with 4-input gates. This leads to a reduction in the power dissipation by 50%. In addition, bandwidths of more than 20 GHz have been obtained for 4-bit and 5-bit ADCs at a sampling frequency of 10 GHz.

Toward the age of ultra-high-density digital ULSI systems, the development of new integrated circuits suitable for an ultimately fine geometry feature size will be an important issue. Resonant-tunneling (RT) diodes and transistors based on quantum effects in deep submicron geometry are such kinds of key devices in the next-generation ULSI systems. From this point of view, there has been considerable interests in RT diodes and transistors as functional devices for circuit applications. Especially, it has been recognized that RT functional devices with multiple peaks in the current-voltage (I-V) characteristic are inherently suitable for implementing multiple-valued circuits such as a multiple-state memory cell. However, very few types of the other multiple-valued logic circuits have been reported so far using RT devices. In this paper, a new multiple-valued programmable logic array (MVPLA) based on RT devices is proposed for the next-generation ULSI-oriented hardware implementation. The proposed MVPLA consists of 3 basic building blocks: a universal literal circuit, an AND circuit and a linear summation circuit. The universal literal circuit can be directly designed by the combination of the RT diodes with one peak in the I-V characteristic, which is programmable by adjusting the width of quantum well in each RT device. The other basic building blocks can be also designed easily using the wired logic or current-mode wired summation. As a result, a highdensity RT-diode-based MVPLA superior to the corresponding binary implementation can be realized. The device-model-based design method proposed in this paper is discussed using static characteristics of typical RT diode models.