Single-Flux-Quantum Bipolar Digital-to-Analog Converter Comprising Polarity-Switchable Double-Flux-Quantum Amplifier

We present a single-flux-quantum (SFQ)-based digital-to-analog converter (DAC) generating bipolar output voltages, in which the key component is a polarity-switchable double-flux-quantum amplifier (PS-DFQA). The DAC comprised a dc/SFQ converter, an 8-bit variable pulse-number-multiplier (PNM), and a 8-fold PS-DFQA integrated on a single chip. SFQ pulse-frequency modulation was employed to realize variable output voltage amplitude, for which the multiplication factor of the variable-PNM was controlled by a commercial data generator situated at room temperature. The variable-PNM realized 8-bit resolution with a multiplication factor between 0 and 255. Bias currents fed to the 8-fold PS-DFQA were polarity-switched in synchronization with the digital code for the variable-PNM. The whole circuits including I/O elements were designed using SFQ cell libraries, and fabricated using a niobium integration process. Sinusoidal bipolar voltage waveform of 0.38 mVpp was demonstrated using a reference signal source of 43.94 MHz

A flexible low-cost, high-precision, single interface electrical impedance tomography system for breast cancer detection using FPGA

Typically, in multi-frequency Electrical Impedance Tomography (EIT) systems, a current is applied and the voltages developed across the subject are detected. However, due to the complexity of designing stable current sources, there has been mention in the literature of applying a voltage to the subject whilst measuring the consequent current flow. This paper presents a comparative study between the two techniques in a novel design suitable for the detection of breast cancers. The suggested instrument borrows the best features of both the injection of current and the application of voltage, circumventing their limitations. Furthermore, the system has a common patient-electrode interface for both methodologies, whilst the control of the system and the necessary signal processing is carried out in a field programmable gate array (FPGA). Through this novel system, wide-bandwidth, low-noise, as well as high-speed (frame rate) can be achieved

Design of an Advanced Programmable Current-Source Gate Driver for Dynamic Control of SiC Device

Silicon carbide (SiC) power devices outperform Silicon-based devices in operational voltage levels, power densities, operational temperatures and switching frequencies. However, the gate oxide of SiC-based device is more fragile compared with its Si counterpart. The vulnerability of the gate oxide in SiC power devices requires the development of a gate driver that is able to have more control during the turn-on and turn-off process. This paper proposes an innovative current-source gate driver where the gate current can be fully programmed. The novelty of the gate driver is that the dynamic switching transients and the static on/off-state can be controlled independently. In order to achieve this approach, a signal decomposition and reconstruction technique is proposed to apply the separate control over the dynamic switching transient and the static on/off-state gate voltage respectively. The fundamental principle of the proposed circuit is verified in simulation. In addition, a prototype of the active gate driver has been built and tested to validate the effectiveness of the flexible control over the gate voltage