Kobchai Dejhan

Accurate CMOS-based current conveyors

An integrable circuit technique for implementing both positive and negative second-generation current conveyors (CCII) is described. Since the proposed circuits consist of a differential pair, current sources, and current mirrors, the realization method can result in a fully integrated current conveyor. The realization method is suitable for fabrication in CMOS technology. The performance of the CMOS-based CCIIs is discussed in detail. The basic performances are demonstrated and simulation and experimental results are presented. The DC transfer characteristics for converting resistors are linear over the total dynamic range. >

An integrable electronic-controlled quadrature sinusoidal oscillator using CMOS operational transconductance amplifier

This paper describes two approaches to implementing third-order oscillators. The first approach proposes a third-order oscillator using transconductors and capacitors. They are cascaded as two lossy and one lossless integrator circuit. This approach is a feedback from transconductance gain = 2. This first circuit is based on a basic transconductor with a simple configuration including 16 ransistors, four current sources and three capacitors. The second approach proposes a third-order oscillator using transconductors, capacitors and a transresistor circuit. These are cascaded as lossy integrator circuits and are fedback with voltage gain = 8. This voltage gain can be designed using a transconductor circuit and a transresistor circuit. This second circuit consists of 18 transistors, four current sources and three capacitors. Since both circuits use no resistors, they are suitable for further fabrication. These circuits use a ±3V power supply.

A full-wave rectifier using a current conveyor and current mirrors

The realization of a full-wave rectifier using a current conveyor and current mirrors is presented. The proposed rectifier is composed of a voltage-to-current converter, a current mode full-wave rectifier, and a current-to-voltage converter. A voltage input signal is changed into a current signal by the voltage-to-current converter. The current mode full-wave rectifier rectifies this current signal resulting in the current full-wave output signal that is converted into a voltage full-wave output signal by one grounded-resistor. The theory of operation is described. The simulation and experiment results are used to verify the theoretical prediction. Simulated results show that the proposed rectifier yields the minimum voltage rectification to 94µV. Experimental results demonstrate the performance of the proposed rectifier for 50mVpeak signal rectification.

DDCC-Based Quadrature Oscillator with Grounded Capacitors and Resistors

A new voltage-mode quadrature oscillator using two differential difference current conveyors (DDCCs), two grounded capacitors, and three grounded resistors is presented. The proposed oscillator provides the following advantages: the oscillation condition and oscillation frequency are orthogonally controlled; the oscillation frequency is controlled through a single grounded resistor; the use of only grounded capacitors and resistors makes the proposed circuit ideal for IC implementation; low passive and active sensitivities. Simulation results verifying the theoretical analysis are also included.

High frequency and high precision CMOS full-wave rectifier

This paper describes a high frequency and high precision full-wave rectifier using a fully differential input and output operational transconductance amplifier (FDIO-OTA), which is very suitable for CMOS technology implementation. The system comprises a voltage to current converter, precision full-wave rectifier and a current-to-voltage converter. An input voltage signal is converted into two symmetrical current signals by using a FDIO-OTA. Two current signals will be rectified by using MOS diodes and convert into output voltage by using grounded MOS resistor. The circuit exhibits a very precise rectifier and very high operating frequency. The simulation results demonstrate the performance of the proposed circuit.

New electronically tunable current-mode universal biquad filter using translinear current conveyors

In this study, a new electronically tunable current-mode universal filter with two inputs and two outputs employing one translinear current conveyor, one translinear current conveyor with controlled current gain and two grounded capacitors is presented. The proposed circuit offers the following attractive features: realisation of low-pass, band-pass, high-pass, band-stop and all-pass current responses from the same configuration; employment of the minimum active and passive components; no requirement of component matching conditions; independent current-control of the parameters natural frequency (ωo) and quality factor (Q); low active and passive sensitivities; and high impedance output. The characteristics of the proposed circuit are simulated using PSPICE to confirm the theory.

Bi-Minimax Design of Even-Order Variable Fractional-Delay FIR Digital Filters

This paper proposes a new minimax method for designing even-order finite-impulse-response (FIR) variable fractional-delay (VFD) digital filters with both the peak errors (maximum absolute errors) of variable frequency response (VFR) and VFD response being minimized. We call such a new minimax design the bi-minimax design, which minimizes a mixed error function that contains both the VFR peak error and VFD peak error. A relative weighting factor is used in the mixed error function for adjusting the relative weightings of the two peak errors. The central part of the biminimax design is how to formulate the biminimax design with highly non-linear constraints on the VFD errors as a solvable one. After linearizing the highly non-linear constraints as linear ones, the biminimax design problem can be easily solved by using the well-known efficient software SeDuMi. As a result, both the VFR peak error and VFD peak error can be simultaneously suppressed and the resulting VFR errors and VFD errors are made nearly equiripple (bi-equiripple). As compared with the existing SOCP-based minimax design that minimizes only the VFR peak error, the proposed biminimax method can achieve a nearly biequiripple design for both the VFR and VFD errors. A design example is given to illustrate the effectiveness of the biminimax design method.

CMOS dual output current mode half-wave rectifier

A CMOS dual output current mode half-wave rectifier is presented. The proposed rectifier is composed of three main components: a dual output V–I converter, two half-wave current rectifiers and two I–V converters. A voltage input signal is changed into two current signals by the V–I converter. The current rectifiers rectify these current signals, resulting in positive and negative half-wave current signals that are converted to positive and negative half-wave voltage signals by the I-Vconverters. The theory of operation is described, and the simulated results obtained from the PSPICE program are used to verify the theoretical prediction. Simulated rectifier performance with a 0.5μm MOSFET model using ±1.2V supply voltage demonstrates good rectifier integrity at operating frequencies up to 100MHz.

Current‐mode quadrature oscillator using current differencing transconductance amplifiers

This article presents a new electronically tunable single‐element‐controlled current‐mode quadrature sinusoidal oscillator circuit using current differencing transconductance amplifiers (CDTAs). The proposed oscillator is consisted of two CDTAs, two grounded capacitors and one grounded resistor, which is beneficial to monolithic integrated circuit implementation both in CMOS and bipolar technologies. The condition of oscillation and the frequency of oscillation are independently controllable. The frequency of oscillation can also be electronically controlled by adjusting the bias current of CDTA. The circuit provides four quadrature current outputs and two quadrature voltage outputs. The current output terminals possess high impedance level. PSPICE simulation results are used to verify the performance of the proposed circuit implemented at the transistor level. The measurement results support the computer simulations.

Electronically tunable voltage-mode universal filter with three-input single-output

A new electronically tunable voltage-mode universal filter with three-input single-output using six simple CMOS operational transconductance amplifiers and two capacitors is proposed. The proposed filter provides lowpass, bandpass, highpass, bandstop and allpass voltage responses. Also, the parameters ωo and Q can be set orthogonally by adjusting the circuit components. The performances of the proposed circuit are simulated with PSPICE to confirm the presented theory.