A novel mixed-mode OTA-C universal filter

A novel mixed-mode biquad circuit is presented. The circuit uses six single-output- and one dual-output-operational transconductance amplifiers, two grounded capacitors; and can realize lowpass, highpass, bandpass, notch, lowpass-notch, highpass-notch and allpass responses from the same topology. The circuit can be driven by voltage or current and its output can be voltage or current. The parameters ω_o and ω_o/Q _o enjoy independent electronic tunability. Simulation results are included.     

Single FDCCII-based mixed-mode biquad filter with eight outputs

The transconductance and the transresistance modes might act as the bridge transferring from voltage-mode to current-mode and vice versa, respectively. A novel mixed-mode (including voltage, current, transconductance, and transresistance modes) biquad filter with one input and seven outputs or two inputs and eight outputs is presented. The proposed filter structure only uses a single fully differential current conveyor (FDCCII), three resistors and two grounded capacitors, which are the least components necessary for realizing voltage, current, transresistance modes all five standard filter functions and transconductance-mode band-pass, high-pass filter functions from eight output terminals. Moreover, the new mixed-mode biquad filter still enjoys (i) the employment of two grounded capacitors (attractive for absorbing shunt parasitic capacitance and ideal for IC implementation), (ii) orthogonal control of ω₀ and Q (easy for tunability), and (iii) high output impedance of three current outputs (good for cascadability). H-Spice simulation results verify the theoretical analysis.     

Pure-Mode Gm−C Biquad Filters*

A continuous time differential voltage mode G_m–C biquad and its adjoint current-mode version are described, employing FCS (floating current source) circuits as building blocks. The biquad operates in the pure mode, i.e. no resistors are used to convert internally voltage into current or vice versa. Both f_p and Q_p are tunable by current sources applied externally. The current mode version is capable of providing values of Q_p 160. Due to the increasing Loop transmission, THD improves significantly towards low frequencies. The input stage of the voltage mode version employs two OTAs, whose outputs are connected in parallel in order to add their differential inputs. This results in the hitherto unnoticed property of subtracting their common mode input, providing an open loop gain which is high for differential, but low for common mode signals.     

New universal filter using only current followers as active elements

A new universal current-mode (CM) biquad filter is presented which can realise all the five standard filter functions namely lowpass, bandpass, highpass, notch and allpass employing only unity-gain current followers (CF) as active elements. The workability of the proposed universal biquad, realised with CMOS unity-gain current followers, is established by SPICE simulations. The new circuit provides explicit CM outputs from high output impedance terminals and possesses a number of advantageous features all of which are not available simultaneously in any of the previously reported CF-based universal biquad filters.     

New voltage-model/current-mode universal biquad filter using unity-gain cells

A new universal biquad filter is presented which can realize all the five standard filter functions namely lowpass, bandpass, highpass, notch and allpass in voltage-mode (VM) as well as in current-mode (CM) employing only unity-gain cells (i.e. voltage followers and current followers) as active elements. Explicit VM/CM outputs are available from low output impedance terminals and high output impedance terminals, respectively. The workability of the proposed universal biquad, realized with CMOS unity-gain cells, is established by SPICE simulations.     

A current-mode biquadratic amplitude equalizer

A boost biquad transfer function with two symmetrical zeros on the real axis is derived; it provides a technique for amplitude equalization with a second-order continuous-timeg _m -C section using current injection. The synthesis procedure yields a differential boost biquad consisting of three double-input OTAs and a single-input high-g _m boost OTA. SPICE simulations show that for boost gain up to 20 dB the phase of the biquad is essentially unaffected. The presented technique is found suitable for amplitude equalization of disk-drive read channels operating in the range of 100 MHz.     

A novel mixed-mode current-conveyor-based filter

A new mixed-mode biquad circuit is presented. The circuit uses six single-output plus-type second-generation current-conveyors (CCII+s), a single dual-output CCII+, two grounded capacitors, eight resistors, at least two of them permanently grounded, and can realize lowpass, highpass, bandpass, notch, lowpass notch, highpass notch and allpass responses from the same topology. The circuit can be driven by voltage or current and its output can be voltage or current. The parameters ω₀ and ω₀/Q ₀ enjoy independent electronic tunability. Simulation results are included.     

A systematic realization of current mode universal biquad filters

A family of current mode universal biquads has been proposed. The biquad filters employ multiple output floating nullor (MOFN) configured as multiple output current conveyors (MOCC). The five-MOFN-based biquad has the property of independently tunable gain, bandwidth, and cut-off frequency without having any passive component matching constraint. Although the four/three MOFN-based universal biquads offer limited tunability of different parameters they do not have any parameter matching constraint on them and in addition, they offer the advantage of reduction in the number of MOFNs and resistances. The workability of all the proposed circuits has been verified using PSPICE simulations based CMOS MOFNs implemented in 0.35?µ CMOS technology.     

A high-linear wide-tunable CMOS transconductor for video frequency applications

In this paper a new CMOS transconductor structure based on a g_m-boosted degenerated differential pair is presented for applications in the video frequency range. The proposed circuit combines two techniques, a switchable array of source degenerating MOS resistors and a programmable output current mirror, in order to widen the G_m tuning range while maintaining linearity. Degeneration MOS resistors are made common-mode voltage independent thanks to a simple control circuit. Post-layout simulation results from a 0.35 μm design supplied at 3.3 V show a wide tuning range (10–100 MHz), good linearity (−58.4 dB for an output signal voltage of 1.1 V_p–p) and low excess phase (<0.5° over the whole tuning range).     

Multi-function biquad using single current differencing transconductance amplifier

An universal multi input single output type multifunction biquad is proposed. The proposed configuration employs only one current differencing transconductance amplifier as the active element, two capacitors and three resistors. The circuit realizes all five filter functions (i.e. Low Pass, High Pass, Band Pass, Notch and All Pass) without changing the circuit topology. The natural frequency ω₀ is independently and electronically tunable. The workability of the proposed multifunction biquad has been verified using SPICE simulation.     

Synergy at work between continuous-time and sampled-data analog filters for integrated high-frequency,high-Q signal processing

High-frequency, high-Q-factor analog signal processing systems based on sampled-data switched-capacitor circuitry and continuous-time filters are proposed in a way that tends to combine the most advantageous aspects of both techniques. The new systems are applicable to video, radio and radar filtering functions and have unparalleled potential for producing more accurate, economical, and repeatable results than have been achieved with other methods.1.F _s is the sampling frequency and M and L are integers.2. A similar model could easily be established for the complementary frequency upconversion operation following the SC filter and involving the SC interpolator and the output CT filter, but this will not be considered here for conciseness.     

A new on-line bandwidth tuning approach for biquad OTA-C filters

A new and general bandwidth (BW) tuning strategy for biquad OTA-C filters is presented. We have taken benefit of the advantages of the classical Phase-Locked Loop (PLL) scheme to on-line tune the central frequency f_o and we have applied it to tune also the bandwidth BW of biquad filters. The proposed design procedure uses only two different sizes of OTAs. This methodology has been applied to five biquad band-pass OTA-C filters, allowing f_o-tuning and BW-tuning in an independent way. Furthermore, the influence of OTA non-idealities is discussed by including compact and general expressions for f_o and BW for all these filters. Simulation results validate our proposal with excellent BW-tuning accuracies: an rms error of 0.73% with respect to the bandwidth desired.     

Single FDCCII-Based Tunable Universal Voltage-Mode Filter

None of the previously reported voltage-mode universal biquad filters with three inputs and a single output offers either of the following two important advantages: (i) the use of only one active element and (ii) independent control of ω₀ and ω₀/Q. In this paper, a novel biquad filter, achieving both of these advantages, is presented. HSPICE simulation results using TSMC025 process and ±1.25 V supply voltages validate the theoretical predictions.     

Versatile voltage-mode universal biquad filter using the operational amplifier pole

A new multifunction voltage-mode biquad filter topology having three inputs and one output is described. The filter consists of a single operational amplifier (OA), a single capacitor, and two resistors and supports LP, BP, HP, AP and Notch filtering signals from the same topology, without requiring additional components besides being devoid of component matching constraints. The filter uses OA pole and has thereby acquired suitability for extended frequency operation. The natural angular frequency ω₀ and the Q can be separately tuned. The circuit has low sensitivity figures. PSPICE simulation results are employed to verify the circuit performance.     

Voltage/Current-Mode Universal Filter Using FTFN and CFA

A novel configuration for realizing voltage/current-mode (VM/CM) universal filter using a single four terminal floating nullor (FTFN), a single current feedback amplifier (CFA), two capacitors and three resistors is presented. The VM configuration has three inputs and a single output and implements all the five generic filtering functions through the selection of inputs. This topology enjoys cascadability and does not require any additional active element for facilitating the filter realizations. The same circuit in current-mode has a single input and four outputs and realizes LP, HP and two BP responses simultaneously from which AP and Notch can also be realized. This topology uses grounded resistors and capacitors which are ideal for monolithic integration. Both the topologies enjoy orthogonal control of natural frequency (ω₀) and quality factor (Q) by the grounded resistors. The topologies enjoy low active and passive sensitivity figures. Experimental and PSPICE simulation results are also included.     

基于MOCCCⅡ-C的二阶多功能电流模式滤波器

提出了一种基于第二代电流控制传输器(CCCⅡ)的电流模式滤波器。电路由2个第二代多输出电流控制传输器(MOCCCⅡs)和2个接地电容构成,通过选择不同的输出端口可以实现高通、带通、低通、带阻、全通的功能。调整MOC-CCⅡs的偏置电流和电容值可以改变特征参数,产生的电路具有很低的灵敏度。最后对引入的MOCCCⅡ及提出的电路进行PSpice仿真。     

Oscillation Test Scheme of SC Biquad Filters Based on Internal Reconfiguration

In this paper, we explore general conditions for the oscillation based test of switched-capacitor biquad filter stages. Expressions describing the characteristics of a filter stage put into oscillation are derived and conditions for achieving oscillation by internal transformation of the filter stage are explored. Reconfiguration scheme based on the transformation of the biquad filter stage to a quadratic oscillator is studied. Theoretically the circuit can be put into oscillation by de-activating a single capacitor. Simulations, however, show that in practice a carefully designed low feed-back loop is required to achieve acceptable oscillation test mode.

Universal voltage-mode filter using only plus-type DDCCs

Despite the extensive literature on current conveyor-based voltage-mode universal biquads with single input and multiple outputs, no filter circuit has been reported to simultaneously achieve all of the advantageous features: (i) employment of only two differential difference current conveyor (DDCC), (ii) employment only two grounded capacitors, (iii) employment only three resistors, (iv) simultaneously realize voltage-mode low-pass, band-pass, high-pass, notch and all-pass filter signals from the five output terminals, respectively, (v) orthogonal control of ω _o and Q, (vi) low input impedance and can be cascadable (vii) no need to employ inverting type input signals, and (viii) no need to impose component choice except realizing the all-pass filter signal.     

Design of transimpedance low-pass filters

The input of a transimpedance filter is a current signal, while its output is a voltage signal. In this article, a design method for a transimpedance filter is introduced. Also, the topologies and calculation methods of the parameters of three biquadratic transimpedance low-pass (LP) filter circuits are presented in detail, according to the value of Q which is low or medium or high. As for the high-order filter, it can be designed by transimpedance LP biquad section as first stage cascaded with voltage-mode LP filters. Finally, to verify the effectiveness of the design, a design example of a high-order transimpedance LP filter is given.     

A FG-MOS Based Fully Differential Current Controlled Conveyor and Its Applications

This paper presents a new fully differential second generation current controlled conveyor (FDCCCII) based on differential pair topology, which employs floating gate MOS transistors (FG-MOS). It uses floating gate MOSFETs at the input stage and has rail-to-rail structure which performs with both positive and negative signals. This circuit has tunable parasitic resistance at its input port. It operates with low supply voltage (±0.8 V), low power consumption (lower than 3 mW at current bias of 1 mA), and wide range parasitic resistance (R _X ). This circuit has less MOSFET than the previous similar circuits and is suitable for integrated circuit design. To demonstrate the application of the proposed circuit, a fully differential current mode LC-ladder filter and a fully differential multifunction biquad filter are designed. Simulation results by HSPICE confirm validity of the proposed circuit and its application.