High Output Impedance Research Articles

Realization of current-mode SC-CNN-based Chua’s circuit

A current-mode State-Controlled Cellular Neural Network (SC-CNN) cell based on current conveyors (CCIIs) and multi-output current conveyors (MOCCII) is presented in this paper. Different from the voltage-mode SC-CNN cell whose state variable is voltage signal, the current-mode SC-CNN cell takes current signal as its state variable. A current-mode SC-CNN-based chaotic circuit is developed by using the suitable connection of three current-mode SC-CNN cells. When compared with the existing voltage-mode chaotic circuits, the proposed current-mode chaotic circuit can operate at higher frequency ranges. In addition to this, state currents can be directly obtained at high impedance outputs of MOCCIIs. Furthermore, all elements in this circuit are grounded, thus it is very suitable for integrated circuit (IC) fabrication. Pspice simulations are given to demonstrate the dynamical behaviors of the proposed circuit and its high frequency performance.

Design of a multi-frequency Bio-Impedance Spectroscopy system Analog Front-End and Digital Back-End with system on-chip implementation

In this paper, the design of an on-board and system on-chip Bio-Impedance Spectroscopy (BIS) mixed-signal system is presented. It consists of a Direct Digital Synthesis Sine-Wave Generator (DDS-SWG), an Analog Front-End (AFE), an Analog-Digital Converter (ADC), and a Digital Back-End implemented on a Field Programmable Gate Array (FPGA). The FPGA drives the ADC, the DDS-SWG, and the LCD. The AFE consists of a high output impedance Load-In-Loop Current Source (LL-CS) and High Common-Mode Rejection Ratio (CMRR) Instrumentation Amplifiers (IA). It uses a simple and straightforward impedance extraction algorithm using division and constant multiplication. Furthermore, a method that extends the AFE implementation to BIS tomography applications is presented offering low power dissipation and more chip area budget. The CMOS implementation of the AFE and the digital ASIC using TSMC 0.18µm 1P6M are also presented. The CMOS AFE has been optimized to dissipate low power even when operating at high frequency. The system forms part of a platform that aims to predict a urolithiasis (urinary stone) event where qualitative measures of K+, Ca2+, Cl− and Na+ concentrations in urine can be obtained through impedance/ conductivity.

A Novel Current–Mode High–Frequency Polyphase Filter using Multi–Output Current Differencing Transconductance Amplifiers

Abstract This paper introduces a novel polyphase filter working at high centre frequency using multi-output current differencing transconductance amplifiers (MOCDTAs). The MOCDTA possesses characteristics of low input impedance, high output impedance, wide work frequency and linearly adjustable transconductance. The proposed filter consists of two MOCDTAs, two grounded capacitors, and no resistors. The features of low input impedance and high output impedance make it suitable for cascade. The bandwidth and centre frequency could be adjusted independently by external bias voltage VC and VCa . The image rejection ratio (IRR) could reach 31.6 dB at the centre frequency of 114 MHz, and its bandwidth could be 11.1 MHz. Besides, the centre frequency could be tuned from 38 MHz to 150 MHz with bandwidth of 20.1 MHz. Simulation results which verify the theory are included.

A new DVCC-based fully cascadable voltage-mode full-wave rectifier

In this paper, a new voltage-mode (VM) full-wave rectifier circuit employing two plus-type differential voltage---current conveyors, two grounded resistors, and two diodes is proposed. The proposed full-wave rectifier enjoys high input impedance and low output impedance; accordingly, it is suitable for direct cascading with other VM circuits without requiring additional buffers. It employs only two grounded resistors which are advantageous for integrated circuit implementations. However, it needs a single resistor-matching condition. It is simulated using SPICE program to verify the theoretical analysis.

Low Voltage Mixed-mode Multi Phase Oscillator Using Single FDCCII

In this paper a new low voltage mixed-mode multiphase quadrature oscillator employing a single fully differential second generation current conveyor, two resistors and two grounded capacitors is proposed. The proposed circuit provides two quadrature voltage outputs and three quadrature current outputs simultaneously. In addition, the proposed circuit has been made load insensitive so that it is capable of providing high output impedance current outputs without using additional current followers. Moreover, the proposed circuit of load insensitive quadrature oscillator provides four phase current outputs and two voltage outputs, simultaneously. Non ideal study is also included. Both the proposed circuits enjoy low active and passive sensitivities. This paper further presents an active-C multiphase oscillator with a single FDCCII and two grounded capacitors. The proposed structures are suitable for low voltage applications. Simulation results using PSPICE program on cadence tool are included.

An Ultra-Low Power Subthreshold CMOS RSSI for Wake-Up Receiver

This paper reports an ultra-low power received signal strength indicator (RSSI) for low frequency (LF) wake-up receiver. Topology theory analysis and subthreshold operation are performed to lower power consumption. Each gain stage of the subthreshold limiting amplifier (LA) employs cascade diode-connected loads to obtain high output impedance while maintaining low power. An offset cancelation circuit with different tail currents, which also operates in the subthreshold region, is employed to reduce the DC offset voltage. Unbalanced source-coupled pairs of subthreshold devices adopted in the full-wave rectification are optimized. A 45[Formula: see text]dB input dynamic range and [Formula: see text][Formula: see text]dB indicating error are achieved at 125[Formula: see text]KHz frequency. The prototype occupies an active area of 0.39[Formula: see text][Formula: see text][Formula: see text]0.28[Formula: see text]mm using CSMC 0.153-[Formula: see text]m complementary metal-oxide-semiconductor (CMOS) technology. With a 1.8[Formula: see text]V supply voltage, the overall current consumption is only 6[Formula: see text][Formula: see text]A.

A First-Order Fully Cascadable Current-Mode Universal Filter Composed of Dual Output CCIIs and a Grounded Capacitor

In this paper, a new first-order current-mode (CM) universal filter employing two dual output second-generation current conveyors (DO-CCIIs), one resistor and a grounded capacitor is proposed. The proposed filter has low input and high output impedances; thus, it can be easily connected with other CM circuits. It can simultaneously realize first-order low-pass (LP) and all-pass (AP) responses and can provide high-pass (HP) response with interconnection of LP and AP responses. It can be tuned electronically by replacing with dual output second-generation current controlled conveyors (DO-CCCIIs) instead of DO-CCIIs and removing the resistor. It has only a resistor but no capacitor connected in series to X terminal of DO-CCII; accordingly, it can be operated at high frequencies. Also, it does not need any critical passive component matching conditions and cancellation constraints. A number of simulation results based on SPICE program are included to exhibit performance, workability and effectiveness of the proposed filter configuration.

Second Order Current-mode Quadrature Oscillators Using OTAs

This article presents new current-mode quadrature oscillator circuits using OTA which are designed from block diagram. The proposed circuits consist of three OTAs and two grounded capacitors. The circuits have high output impedance appropriate for cascade connection application in current mode technique which is capable to directly drive load. The oscillators use only grounded capacitor which is very appropriate for further development into an integrated circuit. In addition, the condition of oscillation can be adjusted orthogonally from the frequency of oscillation. The results of PSPICE simulation program are corresponding to the theoretical analysis.

Comprehensive study of Howland circuit with non-ideal components to design high performance current pumps

Howland circuit is a popular high performance, voltage-controlled current pump, which can both sink and source precise amounts of current and provide high output impedance as well as high frequency bandwidth. In this article, analytical expressions are derived for performance characteristics of non-ideal Howland Current Pump, and it is shown that the main characteristics can be adjusted using three independent parameters: resistors’ scale, feedback ratio, and current sensing resistor’s value. The derived expressions are evaluated by computer simulations, and then are used to design a current pump for an impedance cardiography system, as an example. Performance of the circuit is evaluated based on simulations and experimental tests, and then is compared with several previous designs in the literature. The relationships provide a unified framework for the analysis of different configurations of Howland current pump and can facilitate its design process for different applications with specific performance requirements.

A High Performance Bulk Driven Quasi Floating Gate MOSEFT Based Current Mirror

A high performance low voltage bulk driven quasi floating gate MOS based current mirror has been proposed. The combination of bulk driven and quasi FGMOS decreases the input impedance upto 120Ω which is four times smaller than current mirror based on only bulk driven technique. The bandwidth has also been improved upto 173MHz which is three folds of bandwidth of conventional bulk driven current mirror. Very high output impedance upto 1GΩ is achieved using self cascode technique in output section depending the value of factor m. Small signal analysis of proposed circuit verifies the simulated results. The circuit is simulated using 0.18μm CMOS technology with supply voltage of ±0.3V. The proposed current mirror is highly suitable for low voltage applications.

Current-Controlled CFTA Based Fractional Order Quadrature Oscillators

This paper presents a study of fractional order quadrature oscillators based on current-controlled current follower transconductance amplifiers (CCCFTA). The design realisation and performance of the fractional order quadrature oscillators have been presented. The quadrature oscillators are constructed using three fractional capacitors of orders α = 0.5. The fractional capacitor is not available on the market or in the PSPICE program. Fortunately, the fractional capacitor can be realised by using the approximate method for the RC ladder network approximation. The oscillation frequency and oscillation condition can be electronically/orthogonally controlled via input bias currents. Due to high-output impedances, the proposed circuit enables easy cascading in current-mode (CM). The PSPICE simulation results are depicted, and the given results agree well with the anticipated theoretical outcomes.

A 0.13-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m CMOS Current-Mode All-Pass Filter for Multi-GHz Operation

A CMOS wide-bandwidth first-order current-mode all-pass filter (APF) is discussed. The circuit consists of one transistor, a resistor, a grounded inductor, and a load. When used with a current mirror as the load, the current-mode filter exhibits a high output impedance, which is advantageous from an integration point of view and enables this configuration to be cascaded with current-mode circuits. The operation of the proposed circuit is experimentally validated. The APF implemented in IBM $0.13-\mu {\textrm {m}}$ CMOS was measured to have the pole-zero pair located at 8.32 GHz and to achieve a 55 ps group delay while consuming 19 mW from a 1.5-V supply. This paper experimentally demonstrates a CMOS APF that operates at multi-GHz frequencies and achieves the highest delay-bandwidth products of the published CMOS first-order APFs known to the authors.

Low Voltage High Output Impedance Bulk-Driven Quasi-Floating Gate Self-Biased High-Swing Cascode Current Mirror

A low voltage self-biased high-swing cascode current mirror using bulk-driven quasi-floating gate MOSFET is proposed in this paper. The proposed current mirror bandwidth and especially the output impedance show a significant improvement compared to prior arts. The current mirror presented is designed using bulk-driven and bulk-driven quasi-floating gate N-channel MOS transistors, which helped it to operate at very low supply voltage of $${\pm }0.2\,\hbox {V}$$±0.2V. To achieve high output resistance, the current mirror uses regulated cascode stage followed by super cascode architecture. The small-signal analysis carried out proves the improvement achieved by proposed current mirror. The current mirror circuit operates well for input current ranging from 0 to $$250\,{\upmu }\mathrm{A}$$250μA with good linearity and shows the bandwidth of 285 MHz. The input and output resistances are found as $$240\,\Omega $$240Ω and $$19.5\,\hbox {G}\Omega $$19.5GΩ, respectively. Further, the THD analysis and Monte Carlo simulations carried prove the robustness of proposed current mirror. The complete analysis is done using HSpice on UMC $$0.18\,\upmu \mathrm{m}$$0.18μm technology.

Impact of heavy ion irradiation on CMOS current mirrors based on SOI and bulk Si substrates: mismatch and output impedance

The impact of a single event on the performance of CMOS current mirrors (CMs) is studied experimentally in this paper. Both basic and cascode CMs based on bulk Si and PDSOI substrates are employed to demonstrate the permanent effects of damage generated by heavy-ion strikes. The results show that the mismatch of the CMs (bulk Si/PDSOI basic/cascode CMs) changes after heavy-ion irradiation, which means that the accuracy of the output current may need re-evaluation when CMs are operated in a harsh environment. For output impedance, a drastic reduction of 40% is observed for small (W/L = 0.5 μm/0.25 μm) PDSOI basic CMs. This may limit the application of CMs when high output impedance is required to provide a large gain or common mode rejection ratio. Different types of performance degradation after heavy-ion irradiation are classified, and the characteristics are also statistically compared between different types of CM. The mechanisms of these changes are then discussed and traced back to the damage induced by the random heavy-ion strikes. These results demonstrate the permanent effects of damage generated by heavy-ion strikes in CMOS CMs, and provide insights into the impact of heavy-ion irradiation on analog circuits.

New highly linear tunable transconductor circuits with low number of MOS transistors

ABSTRACTIn this article, two new highly linear tunable transconductor circuits are proposed. The transconductors employ only six MOS transistors operated in saturation region. The second transconductor is derived from the first one with a slight modification. Transconductance of both transconductors can be tuned by a control voltage. Both of the transconductors do not need any additional bias voltages and currents. Another important feature of the transconductors is their high input and output impedances for cascadability with other circuits. Besides, total harmonic distortions are less than 1.5% for both transconductors. A positive lossless grounded inductor simulator with a grounded capacitor is given as an application example of the transconductors. Simulation and experimental test results are included to show effectiveness of the proposed circuits.

Designing a mirrored Howland circuit with a particle swarm optimisation algorithm

ABSTRACTElectrical impedance spectroscopy usually requires a wide bandwidth current source with high output impedance. Non-idealities of the operational amplifier (op-amp) degrade its performance. This work presents a particle swarm algorithm for extracting the main AC characteristics of the op-amp used to design a mirrored modified Howland current source circuit which satisfies both the output current and the impedance spectra required. User specifications were accommodated. Both resistive and biological loads were used in the simulations. The results showed that the algorithm can correctly identify the open-loop gain and the input and output resistance of the op-amp which best fit the performance requirements of the circuit. It was also shown that the higher the open-loop gain corner frequency the higher the output impedance of the circuit. The algorithm could be a powerful tool for developing a desirable current source for different bioimpedance medical and clinical applications, such as cancer tissue characterisation and tissue cell measurements.

Multifunction Current Differencing Cascaded Transconductance Amplifier (MCDCTA) and Its Application to Current-Mode Multiphase Sinusoidal Oscillator

Abstract In this study, a new versatile active element, namely multifunction current differencing cascaded transconductance amplifier (MCDCTA), is proposed. This device which adopts a simple configuration enjoys the performances of low-voltage, low-input and high-output impedance, wide bandwidth etc. It simplifies the design of the current-mode analog signal processing circuit greatly, especially the design of high-order filter and oscillator circuits. Moreover, an example as a new current-mode multiphase sinusoidal oscillator (MSO) using MCDCTA is described in this paper. The proposed oscillator, which employs only one MCDCTA and minimum grounded passive elements, is easy to be realized. It can provide random n (n being odd or even) output current signals and these output currents are equally spaced in phase all at high output impedance terminals. Its oscillation condition and the oscillation frequency can be adjusted independently, linearly and electronically by controlling the bias currents of MCDCTA. The operation of the proposed oscillator has been testified through PSPICE simulation and experimental results.

High accurate and wideband current excitation for bioimpedance health monitoring systems

Current sources are critical for the performance of bioimpedance health monitoring device. The challenging features for a high accuracy and wide bandwidth voltage controlled current source are stable and safe current magnitudes. Corresponding to the typical measurement requirements, it should allow typical load impedances in the range from 100Ω to 10kΩ and have high output impedance of approximately 10MΩ at 5kHz and 1MΩ at high frequencies up to 1MHz without harmonics and influence of stray capacitances. Generalized impedance converters and negative impedance converters help to reduce the influence of stray capacitances. In this study, we compare between two types of voltage controlled current sources for grounded loads: Howland and Tietze circuits. Based on this study, we suggest an improved Howland circuit in inverting dual configuration with a negative feedback using the high bandwidth amplifier AD8021. With this configuration, a better accuracy is reached at higher frequencies up to 1MHz. With the addition of compensation capacitor to the operational amplifier, this circuit configuration is capable to maintain approximately constant current amplitude within an accuracy of less than 0.022% at both low and high frequencies up to 1MHz.

Design and Analysis of High Gain, Low Power and Low Voltage a-Si TFT based Operational Amplifier

This paper investigates on the design of two stage Operational Amplifier (Op-Amp) with NMOS input at differential stage. This low power Op-Amp designed with Amorphous Silicon Thin Film Transistor (a-Si TFT) and MOS transistor. It is observed that the newly designed TFT Op-AMP operates in low voltage at 3V DC, with high gain, high output impedance and high phase margin and moderate power dissipation. A detailed design procedure is carried-out to design the proposed Op-Amp. HSPICE Circuit Simulator is used for simulation. Obtained results are compared with CMOS Op-Amp which uses the same circuit and design procedure. The output behavior of TFT Op-Amp is also compared with the existing work showing good agreement.

Multi-function Current Differencing Cascaded Transconductance Amplifier (MCDCTA) and Its Application to Current-Mode Multiphase Sinusoidal Oscillator

In this study, a new versatile active element, namely multifunction current differencing cascaded transconductance amplifier (MCDCTA) is proposed. The proposed MCDCTA enjoys the advantages of low voltage, low-input and high-output impedance, wide bandwidth etc., and it simplifies the design of the current-mode analog signal processing circuit greatly, especially the design of high-order filter and oscillator circuits. Moreover, an example, a new current-mode multiphase sinusoidal oscillator (MSO) using the proposed MCDCTA is described in this paper. The proposed MSO consists only one MCDCTA and minimum grounded passive elements, it could provide 2n (n ? 2) output current signals with equally phase difference, and the output current signals are all at high output impedance terminals. The oscillation condition and the oscillation frequency of the MSO could be linearly and electronically adjusted by controlling the bias currents of MCDCTA, and it is suitable for variable frequency oscillator application. The operation of the proposed oscillator has been verified through PSPICE simulation and experimental results.