Costas Laoudias

0.5-V fractional-order companding filters

Novel configurations of fractional-order filter topologies, realized through the employment of the concept of companding filtering, are introduced in this paper. As a first step, the design procedure is presented in a systematic algorithmic way, while in the next step, the basic building blocks of sinh-domain and log-domain integrators are presented. Because of the employment of metal-oxide-semiconductor MOS transistors operated in the subthreshold region, the derived filter structures offer the capability for operation in an ultra-low-voltage environment. In addition, because of the offered resistorless realizations, the proposed topologies are reconfigurable, in the sense that the order of the filter could be chosen through appropriate bias current sources. The performance of the derived fractional-order filters has been evaluated through simulation and comparison results using the Analog Design Environment of the Cadence software and MOS transistor parameters provided by the Taiwan Semiconductor Manufacturing Company TSMC 180-nm complementary MOS CMOS process. Copyright

1.5-V Complex Filters Using Current Mirrors

The derivation of complex filter topologies according to leapfrog and topological emulation techniques is presented in this brief, where the employed active elements are low-voltage current mirrors. Thus, the offered benefits are the capability of operating in a modern low-voltage environment, the absence of resistors, and the electronic tuning of the frequency characteristics. A 12th-order complex filter function has been realized by employing the aforementioned techniques, and the performance of the corresponding topologies, fabricated in an Austria Mircro Systems 0.35-μm complementary Metal-Oxide-Semiconductor process, has been experimentally verified.

Low-voltage Bluetooth/ZigBee complex filter using current mirrors

Complex signal processing is an attractive technique for removing the image signals that appear in transceiver architectures. The realization of complex filters is achieved by employing an appropriate transformation to the corresponding conventional real filters. A novel complex filter topology realized by employing current mirrors as active elements is introduced in this paper. Attractive characteristics are the capability of low-voltage operation, the electronic tuning of its frequency response and the absence of passive resistors. A 12th-order complex filter has been designed in order to meet the Bluetooth and ZigBee standard requirements. The performance of the filter has been evaluated through simulation results by employing AMS 0.35μm CMOS process, where the most important performance factors have been considered.

Universal biquad filter topology using low-voltage current mirrors

A single input multiple output biquad filter topology realized using current mirrors as active elements is introduced in this manuscript. The proposed topology simultaneously realizes all the standard transfer functions of a biquad filter without modifying its structure. Some attractive characteristics offered by the proposed topology are the employment of only grounded capacitors as passive elements, the electronic adjustment of the resonant frequency, and the capability for operation under a low-voltage environment. The operation of the proposed topology has been validated through simulation results, where the most important performance factors have been evaluated in the case of a bandpass filter transfer function. Copyright

Low-voltage CMOS current-mode filters using current mirrors: Two alternative approaches

A comparative study of continuous-time analogue filter configurations derived by employing two alternative low-voltage current mirror configurations has been performed in this paper. This is achieved by designing a 5th-order lowpass filter following the operational emulation (leapfrog) technique of the corresponding passive prototype filter. The behavior of the derived filter configurations has been studied through simulation results, where important performance factors have been considered in order to evaluate the benefits offered by each topology.

Integrated filters for short range wireless and biomedical applications

Introduction.- Universe Biquads Using Current Mirrors.- Complex Filters for Short Range Wireless Networks.- Filters for Biomedical Applications.- Electronically Adjustable Current Mirrors.- Conclusions.

Differential voltage current controlled current conveyor with low-voltage operation capability

A novel differential voltage current controlled current conveyor topology is introduced in this article. It has the capability for operating in a low-voltage power supply environment and, also, offers resistorless filter realisations. The main attractive offered benefit is that the handling of AC signals is exclusively performed by nMOS transistors and, thus, the proposed element has capability for high-frequency operation. The performance of the proposed cell has been experimentally verified through the realisation of two 3rd-order filters, derived according to the leapfrog and component substitution methods. The filter topologies have been fabricated through the AMS 0.35 µm CMOS process.

A 5‐Gbps USB3.0 transmitter and receiver linear equalizer

Summary A USB3.0 compatible transmitter and the linear equalizer of the corresponding receiver are presented in this paper. The architecture and circuit design techniques used to meet the strict requirements of the overall link design are explored. Output voltage amplitude and de-emphasis levels are programmable, whereas the output impedance is calibrated to 50Ω. A programmable receiver equalizer is also presented with its main purpose being to compensate for the channel losses; this is employed together with a DC offset compensation scheme. The 6.25-GHz equalizer provides a 10 dB overall gain equalization and 5.5-dB peaking at the maximum gain setting. Designed using a mature and well established 65 nm complementary metal oxide semiconductor process, the layout area is 400 µm × 210 µm for the transmitter core, and 140 µm × 70 µm for the equalizer core. The power consumption is 55 and 4 mW, respectively, from a 1.2 V supply at a data rate of 5 Gbps. The target application for such high-speed blocks is to implement the critical part of the physical layer that defines the signaling technology of SuperSpeed USB3 PHY. However, identical iterations of the circuitry discussed can be used for similar high-speed applications like the PCI express (PCIe). Copyright

Companding Realizations of the Nonlinear Energy Operator

Realizations of the nonlinear energy operator (NEO), using the concept of companding filtering, are introduced and compared in this work. For this purpose, the Log-Domain and Sinh-Domain filtering techniques have been followed. Both topologies are constructed from differentiator and multiplier blocks which have been realized through the utilization of nonlinear transconductor cells. Both of the proposed topologies offer the capability of ultra-low voltage operation, thanks to the employment of MOS transistors in the weak inversion. Considering a single power supply voltage of 0.5 V, the behavior of the proposed NEO realizations has been simulated using the Analog Design Environment of the Cadence software and the design kit of the TSMC 130 nm process. Comparison results show that the Sinh-Domain realization offers a more power efficient design than that offered by the Log-Domain realization.

Comparative Study of Resistorless Filters Using Differential Voltage Current Controlled Current Feedback Operational Amplifiers and Differential Voltage Current Controlled Current Conveyors

Differential Voltage Current Controlled Current Feedback Operational Amplifier is an attractive active element for realizing resistorless filters with a minimum active component count. This is verified through a design example, where a 3rd-order leapfrog filter has been realized using the AMS 0.35 μm CMOS process design kit. The performance of the Differential Voltage Current Controlled Current Feedback Operational Amplifier filter is evaluated and compared with that obtained by the corresponding filter, where Differential Voltage Current Controlled Current Conveyors have been employed.