Linear transformation transistor-only high-order current-mode filters are presented in this Letter. Based on the systematic design procedure, we can realize high-order current-mode filters employing switched-current technique efficiently. Only two kinds of switched-current basic cells are needed in our design to obtain simple architectures. The fifth-order Chebychev lowpass filter is designed to verify the proposed synthesis method. Simulation results that confirm the theoretical analysis are obtained.

A second-generation CMOS current conveyor (CCII) consisting of a rail-to-rail complementary N- and P-channel differential input stage for the voltage input, a class AB push-pull stage for the current input, and current mirrors for the current outputs is developed. The CCII was implemented using a double-poly triple-metal 0.6 µm n-well CMOS process, to confirm its operation experimentally. A prototype chip achieves a rail-to-rail swing 2.4 V under 2.5 V power supplies and shows the exact voltage and current following performances up to 100 MHz. These performances make the CCII proposed herein quite useful for a building block of current-mode circuits. The prototype CCII is applied to current-mode filters to demonstrate the wideband signal processing capabilities.

A new current-mode (CM) multifunction filter with single input and three outputs (SITO) employing only three dual output current conveyors (DO-CCII) and four passive elements is presented. The proposed filter realizes three basic filter functions simultaneously all at high impedance outputs. No component matching is required and all the passive and active sensitivities are low.

This paper describes how to generate, analyze and design a novel current-mode filter model using tunable multiple-output operational transconductance amplifiers and grounded capacitors (MO-OTA-Cs) for synthesizing both transmission poles and zeros. Transfer functions of low-order, high-order, general type, and special type are realized based on the filter model. The theory focuses mainly on establishing a relationship between the cascaded MO-OTA-Cs and the multiple-loop feedback matrix, which makes the structural generation and design formulas. Adopting the theory allows us to systematically generate many interesting new configurations along with some known structures. All the filter architectures contain only grounded capacitors, which can absorb parasitic capacitances and require smaller chip areas than floating ones. The paper also presents numerical design examples and simulation results to confirm the theoretical analysis.

A CMOS fully balanced current-mode filter is presented. A fully balanced current-mode integrator which is the basic building block is implemented by adding a very simple common-mode-rejection mechanism to fully differential one. The fully balanced operation can eliminate even order distortion, which is one of the drawbacks in previous continuous current-mode filter. Moreover, the additional circuit can work as not only common-mode-rejection mechanism but also Q-tuning circuit which compensates lossy elements due to finite output impedance of MOS FET. A prototype fifth-order low-pass lad-der filter designed in a standard digital 0.8µm CMOS process achieved a cut-off frequency (fC) of 100MHz; fC was tunable from 75MHz to 120MHz by varying a reference bias current from 50µA to 150µA. Using a single 3V power supply with a nominal reference current of 100µA, power dissipation per one pole is 30mW. The active filter area was 0.011mm2/pole and total harmonic distortion (THD) was 0.73 [%] at 80MHz, 80µA amplitude signal. Furthermore, by adjusting two bias currents, on chip automatic both frequency and Q controls are easily implemented by typical tuning systems, for example master-slave tuning systems [1].

A design of current-mode continuous-time filters for low voltage and high frequency applications using complementary bipolar current mirror pairs is presented. The proposed current-mode filters consist of simple bipolar current mirrors and capacitors and are quite suitable for monolithic integration. Since the filters are based on the integrator type of realization, the proposed method can be used for a wide range of applications. The frequency of the filters can easily be changed by the DC controlling current. A fifth-order Butterworth and a thirdorder leapfrog filter with tunable cutoff frequencies from 20 MHz to 100 MHz are designed as examples and simulated by SPICE using standard bipolar parameters.