Tattaya Pukkalanun

Resistorless realization of current-mode first-order allpass filter using current differencing transconductance amplifiers

This paper presents a realization of a current-mode first-order allpass filter using two current differencing transconductance amplifiers (CDTAs) as the active components and one virtually grounded capacitor as the only passive component. The proposed filer requires no external resistor and is electronically adjustable by varying the external bias current of the CDTA. No component-matching constraints are required. The circuit realizes both inverting and non-inverting types of allpass filters, and also exhibits high-output impedances, which are easy cascading in the current-mode operation. As an application of the proposed CDTA-based allpass section, a current-mode quadrature oscillator is realized. PSPICE simulation results are given to confirm the theoretical analysis.

Electronically Tunable Single-Input Five-Output Voltage-Mode Universal Filter Using VDTAs and Grounded Passive Elements

This paper presents a possible usage of the voltage differencing transconductance amplifier (VDTA) for the design of an electronically tunable single-input five-output voltage-mode universal filter. The presented filter is constructed using two VDTAs, two capacitors and two resistors that are all grounded. The circuit simultaneously realizes lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP) filtering responses, without changing the circuit topology. The circuit is capable of providing an independent electronic control of the natural angular frequency (ω0) and the quality factor (Q) through the transconductance gains of the VDTAs. By simply adjusting the transconductance ratio, a high-Q filter can also be obtained. Because of the high-input impedance of the circuit, it is advantageous for cascade connection. To support the theoretical analysis, the properties of the designed filter have been verified by PSPICE simulation results.

Structural generation of two integrator loop filters using CDTAs and grounded capacitors

A versatile family of two integrator loop filter structures using current differencing transconductance amplifiers (CDTAs) and grounded capacitors is generated. The basic filter building blocks consist of current proportional blocks, current lossless integrators and a current lossy integrator based on the use of CDTAs as the major active components. It is demonstrated that the derived filter structures can realize a general class of second-order current transfer functions. Since the resulting structures contain only CDTAs and grounded capacitors, they are general and very appropriate for integration, cascading and electronic tuning. The influences of the CDTA non-idealities are also discussed. The functionality of the resulting filters has been verified by simulation results. Copyright

CDBA-Based Universal Biquad Filter and Quadrature Oscillator

The voltage-mode universal biquadratic filter and sinusoidal quadrature oscillator based on the use of current differencing buffered amplifiers (CDBAs) as active components have been proposed in this paper. All the proposed configurations employ only two CDBAs and six passive components. The first proposed CDBA-based biquad configuration can realize all the standard types of the biquadratic functions, that is, lowpass, bandpass, highpass, bandstop, and allpass, from the same topology, and can also provide orthogonal tuning of the natural angular frequency and the bandwidth (BW) through separate virtually grounded passive components. By slight modification of the first proposed configuration, the new CDBA-based sinusoidal quadrature oscillator is easily obtained. The oscillation condition and the oscillation frequency are independently adjustable by different virtually grounded resistors. The sensitivity analysis of all proposed circuit configurations is shown to be low. PSPICE simulations and experimental results based upon commercially available AD844-type CFAs are included, which confirm the workability of the proposed circuits.

SYNTHESIS OF CURRENT DIFFERENCING TRANSCONDUCTANCE AMPLIFIER-BASED CURRENT LIMITERS AND ITS APPLICATIONS

A synthesis of analog current limiter (CL) building blocks based on a current differencing transconductance amplifier (CDTA) is proposed. The breakpoint and the slope of the resulting transfer characteristic obtained from the proposed CDTA-based CL are electronically programmable through the external bias currents. To demonstrate versatility of the proposed electronically tunable CLs, some nonlinear applications to programmable current-mode precision full-wave rectifiers and piecewise-linear function approximation generators are also presented. PSPICE simulation and experimental results confirm the effectiveness of the proposed circuits.

Current-controlled Current-mode Biquadratic Filter with two inputs and three outputs Using Multiple-Output FTFNs

A current-controlled current-mode biquadratic filter using a modified type of a four-terminal floating nullor (FTFN), which is called as an electronically tunable multiple-output FTFN (ET-FTFN), is proposed. The proposed filter with two-input and three-output terminals comprises only ET-FTFNs and four grounded passive elements. The filter can simultaneously realize the inverting-type lowpass, noninverting-type lowpass, inverting-type bandpass, noninverting-type bandpass, highpass, bandstop and allpass filter functions. The natural angular frequency and the quality factor are independently controlled by adjusting the external bias currents of the ET-FTFNs. All the active and passive sensitivities are low. PSPICE simulation results are employed to verify the circuit performance

CCCII-based High-output Impedance Current-mode Universal Filter Employing Only Grounded Capacitors

A current-controlled current-mode universal filter with three inputs and one output using only three current-controlled current conveyors (CCCIIs) and two grounded capacitors is described. The proposed filter provides lowpass, bandpass, highpass, bandstop and allpass current outputs at a high impedance terminal, which enable easy cascadability. The filter also offers an independent electronic control of the natural frequency omega0 and the parameter omega 0/Q through adjusting the bias current of the CCCII. No critical matching condition is required for realizing all the filter responses, and all the incremental parameter sensitivities are low. The performances of the proposed circuit are simulated with PSPICE to confirm the presented theory

Current-mode universal biquad with orthogonal ω o -Q tuning using OTAs

A two-input two-output (TITO) current-mode universal biquad using only four dual-output operational transconductance amplifier (DO-OTAs) and two grounded capacitors is described. By appropriately connecting the input and output terminals, the proposed circuit can provide lowpass, bandpass, highpass, bandstop and allpass current responses. The filter also offers an independent electronic control of the natural frequency (omegao) and the quality factor (Q) through the transconductance gain (gm) of the DO-OTAs. No critical matching conditions are imposed for realizing all the filter responses, and all the incremental parameter sensitivities are low.

CFOA-based single resistance controlled quadrature oscillator

This paper presents a new single-resistance-controlled (SRC) sinusoidal quadrature oscillator with reduce number of passive elements using only two current-feedback operational amplifiers (CFOAs). The proposed oscillator configuration comprising two CFOAs, three resistors and two capacitors provides two sinusoidal voltage outputs in phase quadrature. The circuit has the advantage of independent control of the condition of oscillation and the oscillation frequency through a single resistor. In addition, both proposed circuit configurations have good active and passive sensitivity performance. PSPICE simulation results based on commercially available AD844-type CFOAs are also included, showing the excellent performance of the proposed oscillator configuration.

Resistorless realization of grounded lossy series inductor with two VDBAs and a grounded capacitor

An active simulation of a grounded lossy series RL-type inductor with voltage differencing buffered amplifier (VDBA) is proposed. The proposed inductor is simulated using only two VDBAs, and one grounded capacitor, without any external passive resistors. Also, the simulator requires no critical element matching conditions and cancellation constraints. The realized equivalent resistance and inductance values can be adjusted electronically by means of the VDBA transconductances. The effect of the non-ideal gains of the VDBA on the simulated element values is also discussed in detail. As an application, an active current-mode RLC bandpass filter is designed and simulated using the proposed inductance simulator. The feasibility of the proposed simulator and its filter application has been demonstrated by PSPICE simulations based on TSMC 0.25-μm CMOS technology.