A Novel (DDCC-SFG)-Based Systematic Design Technique of Active Filters

This paper proposes a novel idea for the synthesis of active filters that is based on the use of signal-flow graph (SFG) stamps of differential difference current conveyors (DDCCs). On the basis of an RLC passive network or a filter symbolic transfer function, an equivalent SFG is constructed. DDCCs’ SFGs are identified inside the constructed ‘active’ graph, and thus the equivalent circuit can be easily synthesized. We show that the DDCC and its ‘derivatives’, i.e. differential voltage current conveyors and the conventional current conveyors, are the main basic building blocks in such design. The practicability of the proposed technique is showcased via three application examples. Spice simulations are given to show the viability of the proposed technique

Voltage-Mode Highpass, Bandpass, Lowpass and Notch Biquadratic Filters Using Single DDCC

A new voltage-mode multifunction biquadratic filter using one differential difference current conveyor (DDCC), two grounded capacitors and three resistors is presented. The proposed circuit offers the following attractive advantages: realizing highpass, bandpass, lowpass and notch filter functions, simultaneously, from the same circuit configuration; employing grounded capacitors, which is ideal for integration and simpler circuit configuration

Supplementary Inductance Simulator Topologies Employing Single DXCCII

In this study, six grounded inductance simulator circuits are presented including additional useful features in comparison to previous dual-X current conveyor (DXCCII) based implementations. To demonstrate the performance and usefulness of the presented circuits, one of them is used to construct a fifth order Butterworth high-pass filter and a current-mode multifunction filter as application examples. Simulation results are given to confirm the theoretical analysis. The derived DXCCII and its applications are simulated using CMOS 0.35 μm technology

Chemical Current-Conveyor: a new approach in biochemical computation

Biochemical sensors that are low cost, small in size and compatible with integrated circuit technology play an essential part in the drive towards personalised healthcare and the research described in this thesis is concerned with this area of medical instrumentation. A new biochemical measurement system able to sense key properties of biochemical fluids is presented. This new integrated circuit biochemical sensor, called the Chemical Current-Conveyor, uses the ion sensitive field effect transistor as the input sensor combined with the current-conveyor, an analog building-block, to produce a range of measurement systems. The concept of the Chemical Current-Conveyor is presented together with the design and subsequent fabrication of a demonstrator integrated circuit built on conventional 0.35μm CMOS silicon technology. The silicon area of the Chemical Current-Conveyor is (92μm x 172μm) for the N-channel version and (99μm x 165μm) for the P-channel version. Power consumption for the N-channel version is 30μW and 43μW for the P-channel version with a full load of 1MΩ. The maximum sensitivity achieved for pH measurement was 46mV per pH. The potential of the Chemical Current Conveyor as a versatile biochemical integrated circuit, able to produce output information in an appropriate form for direct clinical use has been confirmed by applications including measurement of (i) pH, (ii) buffer index ( ), (iii) urea, (iv) creatinine and (v) urea:creatinine ratio. In all five cases the device has been demonstrated successfully, confirming the validity of the original aim of this research project, namely to produce a versatile and flexible analog circuit for many biochemical measurement applications. Finally, the thesis closes with discussion of another potential application area for the Chemical Current Conveyor and the main contributions can be summarised by the design and development of the first: ISFET based current-conveyor biochemical sensor, called 'Chemical Current Conveyor, CCCII+' has been designed and developed. It is a general purpose biochemical analog building-block for several biochemical measurements. Real-time buffer capacity measurement system, based on the CCCII+, which exploits the imbedded analog computation capability of the CCCII+. Real-time enzyme based CCCII+ namely, Creatinine-CCCII+ and Urea-CCCII+ for real-time monitoring system of renal system. The system can provide outputs of 3 important parameters of the renal system, namely (i) urea concentration, (ii) creatinine concentration, and (ii) urea to creatinine ratio

Tunable Versatile High Input Impedance Voltage-Mode Universal Biquadratic Filter Based on DDCCs

A high input impedance voltage-mode universal biquadratic filter with three input terminals and seven output terminals is presented. The proposed circuit uses three differential difference current conveyors (DDCCs), four resistors and two grounded capacitors. The proposed circuit can realize all the standard filter functions, namely, lowpass, bandpass, highpass, notch and allpass, simultaneously. The proposed circuit offers the features of high input impedance, using only grounded capacitors, and orthogonal controllability of resonance angular frequency and quality factor

Study of Adjustable Gains for Control of Oscillation Frequency and Oscillation Condition in 3R-2C Oscillator

An idea of adjustable gain in order to obtain controllable features is very useful for design of tuneable oscillators. Several active elements with adjustable properties (current and voltage gain) are discussed in this paper. Three modified oscillator conceptions that are quite simple, directly electronically adjustable, providing independent control of oscillation condition and frequency were designed. Positive and negative aspects of presented method of control are discussed. Expected assumptions of adjustability are verified experimentally on one of the presented solution

Low-Voltage High-Linearity Wideband Current Differencing Transconductance Amplifier and Its Application on Current-Mode Active Filter

A low-voltage high-linearity wideband current differencing transconductance amplifier (CDTA) is presented in this paper. The CDTA consists of a current differencing circuit and a cross-coupling transconductance circuit. The PSPICE simulations of the proposed CDTA show a good performance: -3dB frequency bandwith is about 900 MHz, low power consumption is 2.48 mW, input current linear range is ±100 µA and low current-input resistance is less than 20 Ω, high current-output resistance is more than 3 MΩ. PSpice simulations for a current-mode universal filter and a proposed high-order filter are also conducted, and the results verify the validity of the proposed CDTA

Operational Trans-Resistance Amplifier Based Tunable Wave Active Filter

In this paper, Operational Trans-Resistance Amplifier (OTRA) based wave active filter structures are presented. They are flexible and modular, making them suitable to implement higher order filters. The circuits implement the resistors using matched transistors, operating in linear region, making them well suited for IC fabrication. They are insensitive to parasitic input capacitances and input resistances due to the internally grounded input terminals of OTRA. As an application, a doubly terminated third order Butterworth low pass filter has been implemented, by substituting OTRA based wave equivalents of passive elements. PSPICE simulations are given to verify the theoretical analysis

CMOS current amplifiers : speed versus nonlinearity

This work deals with analogue integrated circuit design using various types of current-mode amplifiers. These circuits are analysed and realised using modern CMOS integration technologies. The dynamic nonlinearities of these circuits are discussed in detail as in the literature only linear nonidealities and static nonlinearities are conventionally considered. For the most important open-loop current-mode amplifier, the second-generation current-conveyor (CCII), a macromodel is derived that, unlike other reported macromodels, can accurately predict the common-mode behaviour in differential applications. Similarly, this model is used to describe the nonidealities of several other current-mode amplifiers because similar circuit structures are common in such amplifiers. With modern low-voltage CMOS-technologies, the current-mode operational amplifier and the high-gain current-conveyor (CCII∞) perform better than open-loop current-amplifiers. Similarly, unlike with conventional voltage-mode operational amplifiers, the large-signal settling behaviour of these two amplifier types does not degrade as CMOS-processes are scaled down. In this work, two 1 MHz 3rd -order low-pass continuous-time filters are realised with a 1.2 μm CMOS-process. These filters use a differential CCII∞ with linearised, dynamically biased output stages resulting in performance superior to most OTA-C filter realisations reported. Similarly, two logarithmic amplifier chips are designed and fabricated. The first circuit, implemented with a 1.2 μm BiCMOS-process, uses again a CCII∞. This circuit uses a pn-junction as a logarithmic feedback element. With a CCII∞ the constant gain-bandwidth product, typical of voltage-mode operational amplifiers, is avoided resulting in a constant 1 MHz bandwidth with a 60 dB signal amplitude range. The second current-mode logarithmic amplifier, based on piece-wise linear approximation of the logarithmic function by a cascade of limiting current amplifier stages, is realised in a standard 1.2 μm CMOS-process. The limiting level in these current amplifiers is less sensitive to process variation than in limiting voltage amplifiers resulting in exceptionally low temperature dependency of the logarithmic output signal. Additionally, along with this logarithmic amplifier a new current peak detectoris developed.reviewe

Novel Current-Mode Sensor Interfacing and Radio Blocks for Cell Culture Monitoring

Since 2004 Imperial College has been developing the world’s first application-specific instrumentation aiming at the on-line, in-situ, physiochemical monitoring of adult stem cell cultures. That effort is internationally known as the ‘Intelligent Stem Cell Culture Systems’ (ISCCS) project. The ISCCS platform is formed by the functional integration of biosensors, interfacing electronics and bioreactors. Contrary to the PCB-level ISCCS platform the work presented in this thesis relates to the realization of a miniaturized cell culture monitoring platform. Specifically, this thesis details the synthesis and fabrication of pivotal VLSI circuit blocks suitable for the construction of a miniaturized microelectronic cell monitoring platform. The thesis is composed of two main parts. The first part details the design and operation of a two-stage current-input currentoutput topology suitable for three-electrode amperometric sensor measurements. The first stage is a CMOS-dual rail-class AB-current conveyor providing a low impedancevirtual ground node for a current input. The second stage is a novel hyperbolic-sinebased externally-linear internally-non-linear current amplification stage. This stage bases its operation upon the compressive sinh−1 conversion of the interfaced current to an intermediate auxiliary voltage and the subsequent sinh expansion of the same voltage. The proposed novel topology has been simulated for current-gain values ranging from 10 to 1000 using the parameters of the commercially available 0.8μm AMS CMOS process. Measured results from a chip fabricated in the same technology are also reported. The proposed interfacing/amplification architecture consumes 0.88-95μW. The second part describes the design and practical evaluation of a 13.56MHz frequency shift keying (FSK) short-range (5cm) telemetry link suitable for the monitoring of incubated cultures. Prior to the design of the full FSK radio system, a pair of 13.56MHz antennae are characterized experimentally. The experimental S-parameter-value determination of the 13.56MHz wireless link is incorporated into the Cadence Design Framework allowing a high fidelity simulation of the reported FSK radio. The transmitter of the proposed system is a novel multi-tapped seven-stage ring-oscillator-based VCO whereas the core of the receiver is an appropriately modified phase locked loop (PLL). Simulated and measured results from a 0.8μm CMOS technology chip are reported