A low-power, second-order Δ/Σ modulator using a single class-AB op-amp for voice-band applications

The design of a power-efficient second-order Δ/Σ modulator for voice-band is presented. At system level, a new single-loop, single-stage modulator is proposed. The modulator employs only one class-AB op-amp to realize a second-order noise shaping for voice-band applications. The modulator is designed in a 0.25μm standard CMOS process, and exhibits 86 dB dynamic range (DR) for a 4 kHz voice-bandwidth. The proposed modulator consumes 125μW from a 2.5 V supply. Aminghasem Safarian received the B.S. and M.S. degrees in electrical engineering from the Sharif University of Technology, in 2000, 2002, respectively. Since 2003 he is a research assistant at University of California, Irvine, working toward his Ph.D. degree in electrical engineering emphasizing on RF IC design for wireless communication systems. During the summer of 2005, he was with Broadcom Corporation, Irvine, CA, where he developed integrated receivers for RFID and WCDMA applications. Farzad Sahandiesfanjani was born in Tabriz, Iran in 1976. He received the B.S. and M.S. degrees in electronics from Sharif University of Technology, Tehran, Iran, in 1998 and 2000, respectively. The subject of his thesis was the design of 4th order cascade delta-sigma modulator for ADSL Analog Front End. From 1998 to 2003, he was with Emad Semicon Co., Tehran, Iran, where he designed circuits for voice application such as CODEC and SLIC chip. He also designed a 3rd order single loop class-D delta-sigma modulator for audio application. He joined Tripath Technology Inc., San Jose, CA, in 2003 and has been working on the design of analog and mixed-signal circuits for class-T audio power amplifier. He is also author of one patent for inductor-less switching audio power amplifier and also co-author of 3 more pending patents and 4 papers. Payam Heydari (S'98–M'00) received the B.S. and M.S. degrees (with honors) in electrical engineering from the Sharif University of Technology, in 1992, 1995, respectively. He received the Ph.D. degree in electrical engineering from the University of Southern California, in 2001. During the summer of 1997, he was with Bell-Labs, Lucent Technologies, Murray Hill, NJ, where he worked on noise analysis in deep submicron very large-scale integrated (VLSI) circuits. During the summer of 1998, he was with IBM T. J. Watson Research Center, Yorktown Heights, NY, where he worked on gradient-based optimization and sensitivity analysis of custom-integrated circuits. Since August 2001, he has been an Assistant Professor of Electrical Engineering at the University of California, Irvine, where his research interest is the design of high-speed analog, radio-frequency (RF), and mixed-signal integrated circuits. Dr. Heydari has received the 2005 National Science Foundation (NSF) CAREER Award, the 2005 IEEE Circuits and Systems Society Darlington Award, the 2005 Henry Samueli School of Engineering Teaching Excellence Award, the Best Paper Award at the 2000 IEEE International Conference on Computer Design (ICCD), the 2000 Honorable Award from the Department of EE-Systems at the University of Southern California, and the 2001 Technical Excellence Award in the area of Electrical Engineering from the Association of Professors and Scholars of Iranian Heritage (APSIH). He was recognized as the 2004 Outstanding Faculty at the EECS Department of the University of California, Irvine. His name was included in the 2006 Who's Who in America. Dr. Heydari is an Associate Editor of the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—part I. He currently serves on the Technical Program Committees of Custom Integrated Circuits Conference (CICC), International Symposium on Low-Power Electronics and Design (ISLPED), International Symposium on Quality Electronic Design (ISQED), and the Local Arrangement Chair of the ISLPED conference. He was the Student Design Contest Judge for the DAC/ISSCC Design Contest Award in 2003, the Technical Program Committee member of the IEEE Design and Test in Europe (DATE) from 2003 to 2004, and International Symposium on Physical Design (ISPD) in 2003. Mojtaba Atarodi received his Ph.D degree from USC (the University of Southern California, Los Angeles), in electrical engineering Electro-physics in 1993, his M.S from University of California at Irvine, and his B.SEE from the Tehran Polytechnic University with first Grade honor. Following his Ph.D completion, he was with Linear Technology Corporation from 1993 to 1996 as an analog design engineer. He has been with Sharif University of Technology as an Assistant and Visiting Professor since 1997. The Author of more than 50 technical journal and conference papers an a book on Analog CMOS IC Design, Dr Atarodi’s main research interests are analog and RF IC system, circuit, and signal processing design as well as analog synthesis tools. Having held several management and consulting positions during the last 15 years in the US industry, he holds one US patent in analog highly linear tunable Operational Transconductance Amplifiers and has applied for 5 more US patents as well.     

CMOS wideband analogue delay stage

A new second-order all-pass filter with maximum achievable delay-bandwidth-product (DBW) is presented. The proposed circuit will be used as a wideband delay element in impulse radio ultra-wideband transceivers. Benefiting from a simple architecture, the proposed circuit achieves a 60 ps delay across a 10 GHz bandwidth, which is the largest delay ever reported over such a wide bandwidth. In addition, the most noticeable advantage of this delay circuit is the small variation of group delay across a wide frequency range, which means negligibly small phase distortion introduced by the circuit     

Panx1b Modulates the Luminance Response and Direction of Locomotion in the Zebrafish

Pannexin1 (Panx1) can form ATP-permeable channels that play roles in the physiology of the visual system. In the zebrafish two ohnologs of Panx1, Panx1a and Panx1b, have unique and shared channel properties and tissue expression patterns. Panx1a channels are located in horizontal cells of the outer retina and modulate light decrement detection through an ATP/pH-dependent mechanisms and adenosine/dopamine signaling. Here, we decipher how the strategic localization of Panx1b channels in the inner retina and ganglion cell layer modulates visually evoked motor behavior. We describe a panx1b knockout model generated by TALEN technology. The RNA-seq analysis of 6 days post-fertilization larvae is confirmed by real-time PCR and paired with testing of locomotion behaviors by visual motor and optomotor response tests. We show that the loss of Panx1b channels disrupts the retinal response to an abrupt loss of illumination and it decreases the larval ability to follow leftward direction of locomotion in low light conditions. We concluded that the loss of Panx1b channels compromises the final output of luminance as well as motion detection. The Panx1b protein also emerges as a modulator of the circadian clock system. The disruption of the circadian clock system in mutants suggests that Panx1b could participate in non-image forming processes in the inner retina.     

On the Dynamics of Regenerative Frequency Dividers

A comprehensive analytical study of regenerative frequency dividers (RFD) is presented. The study includes two fundamental modes of operation in RFDs, namely locked (or stable) and quasi-locked modes, and the study also covers the transition from free-running oscillation to quasi-locked, and ultimately to locked operation mode. Differential equations characterizing the RFD behavior for both operation modes as well as the transition between the two are derived. An RFD circuit for Bluetooth applications was designed and fabricated in a 65-nm CMOS process with a supply voltage of 1.2 V. Measurement results of the RFD prototype verify the accuracy of the proposed analytical models     

A Two-Point Modulation Technique for CMOS Power Amplifier in Polar Transmitter Architecture

A two-point modulation technique is presented that improves the performance of nonlinear power amplifiers (PAs) in polar transmitters. In this scheme, the output amplitude modulation is performed by controlling the current of the PA. The current control technique enables the PA to provide wideband amplitude modulation, as well as high power control dynamic range. In addition, the supply voltage of the PA is adjusted based on the output power level. The voltage supply adjustment substantially improves the effective power efficiency of the PA. The voltage supply control is performed using a second-order sigma-delta dc-dc converter, which presents an efficiency of over 95% in its operational range. The PA operates at 900 MHz with maximum output power of 27.8 dBm and power efficiency of 34% at maximum output power. The proposed PA achieves 62-dB power control dynamic range with amplitude modulation bandwidth of over 17.1 MHz. The circuits are fabricated in a CMOS 0.18 mum process with a 3.3-V power supply.     

Liquidus of Silicon Binary Systems

Thermodynamic knowledge about liquid silicon is crucial for the production of solar-grade silicon feedstock from molten silicon. In the current study, liquidus for silicon binary alloys is formulated using a previously developed method in which the liquidus curve is calculated using two constants. The liquidus measurements for the silicon portion of the silicon alloys with Al, Ca, Mg, Fe, Ti, Zn, Cu, Ag, Au, Pt, Sn, Pb, Bi, Sb, Ga, In, Ni, Pd, Mn, and Rh are reviewed, and the consistent data were used to determine the liquidus constants. The liquidus curves for silicon binary systems are calculated and plotted. It is indicated that the calculated liquidus curves fit well with the experimental data. A correlation between the determined liquidus constants is also observed, which can be used to gain a better understanding of the thermodynamics of the silicon binary melts.