Discrete Circuit Components Research Articles

Locally Active Memristor-Based Neuromorphic Circuit: Firing Pattern and Hardware Experiment

Analog circuit implementation of neuron model is an essential category of neuromorphic circuit since it can reproduce neuron firing patterns and assist in exploring neuron-based applications. The neuron models built by electrophysiological ion transport mechanism can effectively mimic the neuron firing patterns. However, they are rather difficult to implement on analog level because these neuron models involve complex exponential nonlinearities for characterizing the ion channels. Thanks to the superiorities of locally active memristor in constructing artificial neuron circuit, two locally active memristors are employed to characterize the sodium and potassium ion channels and then a memristive neuromorphic circuit is successfully built in this paper. Numerical simulations demonstrate that the memristive neuromorphic circuit can generate abundant firing patterns with respect to memristor-and stimulus-related parameters. Moreover, quasi-periodic bifurcation behavior and coexisting firing patterns are triggered by different memristor initial conditions. Employing off-the-shelf discrete circuit components, a PCB-based analog circuit is manually constructed and hardware experiments are executed. Experimental results captured from hardware measurements satisfactorily verify the numerically simulated ones and effectively show the feasibility of the memristive neuromorphic circuit in generating neuron firing patterns.

Firing pattern in a memristive Hodgkin–Huxley circuit: Numerical simulation and analog circuit validation

Spiking firing patterns and their hardware implementation can assist us in exploring spike-based applications. The classical Hodgkin–Huxley circuit can generate spiking firing patterns, but it is hard to implement on analog platform because of the involvement of complex exponential nonlinearities for characterizing the sodium and potassium ion channels. To solve this issue, this paper proposes a second-order local active memristor (LAM) and a first-order LAM to respectively characterize the sodium and potassium ion channels in the Hodgkin–Huxley circuit, thereby obtains a memristive Hodgkin–Huxley circuit. Numerical simulations demonstrate that the memristive Hodgkin–Huxley circuit can generate abundant spiking firing patterns, i.e. periodic and chaotic spiking firing patterns. These abundant firing patterns can be effectively regulated by memristor- and stimulus-related parameters. Moreover, a PCB-based analog circuit employing off-the-shelf discrete circuit components is manually constructed and hardware experiments are executed. Experimental results captured from hardware measurements satisfactorily verify the numerically simulated spiking firing patterns and effectively exhibit the availability of the memristive Hodgkin–Huxley circuit in generating spiking firing patterns.

A new CCII based meminductor emulator circuit and its experimental results

Due to their many advantages, memelements are a prominent research topic among scientists. Nevertheless, creating emulator circuits is necessary because of the issues with memelements availability. In this paper, a new CCII-based meminductor emulator circuit is presented. The circuit is composed of a few active and passive circuit elements. In order to demonstrate the performance of the proposed circuit, we applied to different analysis types such as at different operating frequencies, temperatures, Monte Carlo, worst case analysis and non-volatility test. In addition to the simulation results, the circuit was built using discrete circuit components, experimental results were examined. The proposed meminductor emulator circuit has a variety of significant advantages, including a simple construction, suitability for implementation in discrete circuits, and great performance in the analysis of both simulation and experimental results.

Universal Service Systems for Scalable Copper Packaging of Discrete Circuit Components

In the decade of digital electronics, no matter what type is, high-value, high-complexity, high-performance devices (such as the main microprocessor core in smart phones) is undoubtedly crucial. However, simple discrete circuit components (such as capacitors, resistors, diodes, transistors, etc.) are also essential for mobile phones. In order to continue to increase functionality and reliability, reduce size and power consumption, reduce costs, and any function we seek in electronic equipment, there is always the basic principle of squeezing everything onto the same semiconductor chip. However, in some unavoidable situations, not all circuit components can run on the same chip. This service system uses a copper substrate as the core material for packaging, and can package chips with high bonding density. It provides a universal service platform for packaged products called: Scalable Universal Copper-based Packaging (CopperPak) service system. This service system is attributed to copper-based packaging (CopperPak) as a solution for expansion packaging, which can package the chip on the multifunctional component as much as possible. Scalable universal copper-based packaging (CopperPak) service system, including miniature copper-based packaging (TyniCopk) and large-scale copper-based packaging (MassyCopk) modules, used to package discrete circuit components, not only solve the discrete circuit components size, heat transfer and positioning alignment issues, and simplify the packaging process and improve yield rate.

An air core pulse transformer with a linearly integrated primary capacitor bank to achieve ultrafast charging

An air core transformer that linearly integrates a capacitor bank as well as a selfclosing switch into the primary winding (LIP) was designed to achieve ultrafast charging. Limiting stray inductance and maximizing the uncoupled dual resonance of the primary and secondary windings were the primary design criteria. To show this concept, two transformers with an uncoupled resonant frequency of approximately 8 MHz were designed for a low voltage output (several kV) and a high voltage output (>100 kV). The design was simulated in a Multisim discrete circuit model and a CST hybrid model which includes the transformer's 3-D structure as well as discrete circuit components. The discrete output (voltage and current) as well as the distributed parameters (electric field distribution and surface current density distribution) for the transformer were obtained. These designs were validated by experimental results. We show that their respective resonance characteristic and voltage gain are accurately predicted by the simulated values, demonstrating the design procedure is valid for both low voltage and high voltage applications. For the high voltage transformer, it has a voltage gain of 3-4. The maximum output voltage was tested up to 120 kV. A charging pulse with a rise time of less than 100 ns was obtained.

A spiking and bursting neuron circuit based on memristor

In this paper, we propose two emulator circuits. Firstly, we present a novel memristor emulator based on operational transconductance amplifier (OTA) which is different from classical TiO2 memristor. This memristor emulator has a threshold switching mechanism. Secondly, we create a novel neuron circuit using proposed memristor, which is capable of generating spiking and bursting firing behaviors, with a biologically plausible spike shapes. The behavior of this neuron circuit can be adjusted by changing only one external biasing voltage. This neuron circuit mimics the behavior of cortical neurons, such as regular spiking (RS), intrinsic bursting (IB), chattering (CH) and fast spiking (FS). Proposed emulator circuits are compatible with VLSI systems and they can also be implemented by using discrete circuit components for different applications.

Simultaneous piston position and tilt angle sensing for large vertical displacement micromirrors by frequency detection inductive sensing

This paper presents a frequency detection based inductive eddy current sensing mechanism to simultaneously sense the piston position and tilt angle of the mirror plate of large vertical displacement micromirrors that exhibit piston scan ranges above 100 μm. This is accomplished by sensing the inductance change, and thus resonant frequency shift, of two microfabricated sensing coils packaged underneath the mirror plate. For demonstration purpose, the coils were paired with discrete circuit components to oscillate at 11.9 MHz and 12.5 MHz, respectively. The piston position and tilt angle of the mirror plate could be simultaneously monitored over a 500 μm piston scan range, achieving a maximum piston sensitivity of 4.15 kHz/μm with a piston sensing resolution of 96 nm and a maximum tilt angle sensitivity of 60.5 kHz/° with a tilt angle sensing resolution of 0.0013°. Analytical modeling of the coil inductance change via image theory was also conducted, showing that the sensor sensitivity and resolution could be improved by increasing the coil oscillation frequency and decreasing the coil size.

Bio-impedance characterization technique with implantable neural stimulator using biphasic current stimulus.

Knowledge of the bio-impedance and its equivalent circuit model at the electrode-electrolyte/tissue interface is important in the application of functional electrical stimulation. Impedance can be used as a merit to evaluate the proximity between electrodes and targeted tissues. Understanding the equivalent circuit parameters of the electrode can further be leveraged to set a safe boundary for stimulus parameters in order not to exceed the water window of electrodes. In this paper, we present an impedance characterization technique and implement a proof-of-concept system using an implantable neural stimulator and an off-the-shelf microcontroller. The proposed technique yields the parameters of the equivalent circuit of an electrode through large signal analysis by injecting a single low-intensity biphasic current stimulus with deliberately inserted inter-pulse delay and by acquiring the transient electrode voltage at three well-specified timings. Using low-intensity stimulus allows the derivation of electrode double layer capacitance since capacitive charge-injection dominates when electrode overpotential is small. Insertion of the inter-pulse delay creates a controlled discharge time to estimate the Faradic resistance. The proposed method has been validated by measuring the impedance of a) an emulated Randles cells made of discrete circuit components and b) a custom-made platinum electrode array in-vitro, and comparing estimated parameters with the results derived from an impedance analyzer. The proposed technique can be integrated into implantable or commercial neural stimulator system at low extra power consumption, low extra-hardware cost, and light computation.

Use of squared magnitude function in approximation and hardware implementation of SISO fractional order system

This paper uses squared magnitude function and genetic algorithm (GA) to propose a generalized method for rational approximation of stable minimum phase fractional order transfer functions (FOTF). The unknown coefficients of an approximant are obtained by equating the squared magnitude of the approximant with that of the FOTF at frequency points (over a specified bandwidth) that are chosen optimally by using GA. Two FOTFs have been approximated by using the proposed method and one of the approximants has been realized in hardware using available discrete circuit components. The results of approximation and circuit realization strongly demonstrate the application of this work in approximation and/or realization of fractional order systems specifically, fractional order controller and filter of higher order.

A biopsy tool with integrated piezoceramic elements for needle tract cauterization and cauterization monitoring

This paper reports the feasibility of biopsy needle tract cauterization and cauterization monitoring using an embedded array of piezoceramic microheaters. Circular heaters of lead zirconate titanate (PZT-5A), with 200μm diameter and 70-80μm thickness, are fabricated using a batch mode micro ultrasonic machining process. These are then assembled into cavities in the walls of 20-gauge stainless steel needles and sealed with epoxy. Experiments are performed by inserting the proposed biopsy needle into porcine tissue samples. The needle surface exceeds the minimum target temperature rise of 33°C for either radial or thickness mode vibrations. The corresponding input power levels are 236mW and 325mW, respectively. The tissue cauterization extends 1-1.25mm beyond the perimeter of the needle and is uniform in all directions. After cauterization, the fundamental anti-resonance frequency and the corresponding impedance magnitude of the PZT heater decrease by 4.1% and 42.6%, respectively, thereby providing a method to monitor the extent of tissue cauterization. A sensing interface circuit capable of measuring the resonance frequency shift of the PZT elements is built and tested using discrete integrated circuit components. The circuit detects the resonance frequency shift from 8.22MHz to 7.96MHz of the PZT elements when the biopsy needle is inserted into wax medium. An interface circuit for actuation of the PZT elements for tissue cauterization is also described.

A Hermetic Wireless Subretinal Neurostimulator for Vision Prostheses

A miniaturized, hermetically encased, wirelessly operated retinal prosthesis has been developed for preclinical studies in the Yucatan minipig, and includes several design improvements over our previously reported device. The prosthesis attaches conformally to the outside of the eye and electrically drives a microfabricated thin-film polyimide array of sputtered iridium oxide film electrodes. This array is implanted into the subretinal space using a customized ab externo surgical technique. The implanted device includes a hermetic titanium case containing a 15-channel stimulator chip and discrete circuit components. Feedthroughs in the case connect the stimulator chip to secondary power and data receiving coils on the eye and to the electrode array under the retina. Long-term in vitro pulse testing of the electrodes projected a lifetime consistent with typical devices in industry. The final assembly was tested in vitro to verify wireless operation of the system in physiological saline using a custom RF transmitter and primary coils. Stimulation pulse strength, duration, and frequency were programmed wirelessly from a Peripheral Component Interconnect eXtensions for Instrumentation (PXI) computer. Operation of the retinal implant has been verified in two pigs for up to five and a half months by detecting stimulus artifacts generated by the implanted device.

Communication and control system for a 15-channel hermetic retinal prosthesis

A small, hermetic, wirelessly-controlled retinal prosthesis has been developed for pre-clinical studies in Yucatan minipigs. The device was attached conformally to the outside of the eye in the socket and received both power and data wirelessly from external sources. Based on the received image data, the prosthesis drove a subretinal thin-film polyimide array of sputtered iridium oxide stimulating electrodes. The implanted device included a hermetic titanium case containing a 15-channel stimulator and receiver chip and discrete circuit components. Feedthroughs in the hermetic case connected the chip to secondary power- and data-receiving coils, which coupled to corresponding external power and data coils driven by power amplifiers. Power was delivered by a 125 kHz carrier, and data were delivered by amplitude shift keying of a 15.5 MHz carrier at 100 kbps. Stimulation pulse strength, duration and frequency were programmed wirelessly from an external computer system. The final assembly was tested in vitro in physiological saline and in vivo in two minipigs for up to five and a half months by measuring stimulus artifacts generated by the implant's current drivers.

Energy and timing measurement with time-based detector readout for PET applications: Principle and validation with discrete circuit components

A new signal processing method for PET application has been developed, with discrete circuit components to measure energy and timing of a gamma interaction based solely on digital timing processing without using an amplitude-to-digital convertor (ADC) or a constant fraction discriminator (CFD). A single-channel discrete component time-based readout (TBR) circuit was implemented in a PC board. Initial circuit functionality and performance evaluations have been conducted. Accuracy and linearity of signal amplitude measurement were excellent, as measured with test pulses. The measured timing accuracy from test pulses reached to less than 300 ps, a value limited mainly by the timing jitter of the prototype electronics circuit. Both suitable energy and coincidence timing resolutions (∼18% and ∼1.0 ns) have been achieved with 3×3×20 mm 3 LYSO scintillator and photomultiplier tube-based detectors. With its relatively simple circuit and low cost, TBR is expected to be a suitable front-end signal readout electronics for compact PET or other radiation detectors requiring the reading of a large number of detector channels and demanding high performance for energy and timing measurement.

Implementation of an elaborated neuromorphic model of a biological photoreceptor

We describe here an elaborated neuromorphic model based on the photoreceptors of flies and realised in both software simulation and hardware using discrete circuit components. The design of the model is based on optimisations and further elaborations to the mathematical model initially developed by van Hateren and Snippe that has been shown to accurately simulate biological responses in simulations under both steady-state and limited dynamic conditions. The model includes an adaptive time constant, nonlinear adaptive gain control, logarithmic saturation and a nonlinear adaptive frequency response mechanism. It consists of a linear phototransduction stage, a dynamic filter stage, two divisive feedback loops and a static nonlinearity. In order to test the biological accuracy of the model, impulses and step responses were used to test and evaluate the steady-state characteristics of both the biological (fly) and artificial (new neuromorphic model) photoreceptors. These tests showed that the model has faithfully captured most of the essential characteristics of the insect photoreceptor cells. The model showed a decreasing response to impulsive stimuli when the background intensity was increased, indicating that the circuit adapted to background luminance in order to improve the overall operating range and better encode the contrast of the stimulus rather than luminance. The model also showed the same change in its frequency response characteristics as the biological photoreceptors over a luminance range of 70,000 cd/m(2), with the corner frequency of the circuit ranging from 10 to 90 Hz depending on the current state of adaptation. Complex naturalistic experiments have also further proven the robustness of the model to perform in real-world scenario. The model showed great correlation to the biological photoreceptors with an r (2) value exceeding 0.83. Our model could act as an excellent platform for future experiments that could be carried out in scenarios where in vivo intracellular recording from biological photoreceptors would be impractical or impossible, or as a front-end for an artificial imaging system.

The circuit realization of Mexican Hat wavelet function

A wavelet network circuit implementation for Mexican Hat mother wavelet has been proposed for nonlinear function approximation which can also be used for the realization of the algebraic nonlinear components. The Mexican Hat mother wavelet function has been implemented with discrete circuit components and it has been observed that the experimental waveform obtained from the realized circuit is approximately same as the Spice simulation of the original function. The circuit simulations of exemplar functions implemented in Spice are also given.