A 12-bit 75-MS/s pipelined ADC using open-loop residue amplification

Precision amplifiers dominate the power dissipation in most high-speed pipelined analog-to-digital converters (ADCs). We propose a digital background calibration technique as an enabling element to replace precision amplifiers by simple power-efficient open-loop stages. In the multibit first stage of a 12-bit 75-MSamples/s proof-of-concept prototype, we achieve more than 60% residue amplifier power savings over a conventional implementation. The ADC has been fabricated in a 0.35-/spl mu/m double-poly quadruple-metal CMOS technology and achieves typical differential and integral nonlinearity within 0.5 LSB and 0.9 LSB, respectively. At Nyquist input frequencies, the measured signal-to-noise ratio is 67 dB and the total harmonic distortion is -74 dB. The IC consumes 290 mW at 3 V and occupies 7.9 mm/sup 2/.     

Digitally Assisted Analog Circuits

Today's interfaces between digital and "real world" analog signals rely mainly on complex analog circuit components that strictly limit achievable power efficiency and throughput. Digitally assisted analog circuits can exploit digital circuits' high density and low energy per computation to enable a new generation of interface electronics based on minimal-precision, low-complexity analog building blocks.     

Supratentorial pilocytic astrocytomas, astrocytomas, anaplastic astrocytomas and glioblastomas are characterized by a differential expression of S100 proteins

The levels of expression of the S100A1, S100A2, S100A3, S100A4, S100A5, S100A6 and S100B proteins were immunohistochemically assayed and quantitatively determined in a series of 95 astrocytic tumors including 26 World Health Organization (WHO) grade I (pilocytic astrocytomas), 23 WHO grade II (astrocytomas), 25 WHO grade III (anaplastic astrocytomas) and 21 WHO grade IV (glioblastomas) cases. The level of the immunohistochemical expression of the S100 proteins was quantitatively determined in the solid tumor tissue (tumor mass). In addition twenty blood vessel walls and their corresponding perivascular tumor astrocytes were also immunohistochemically assayed for 10 cases chosen at random from each of the four histopathological groups. The data showed modifications in the level of S100A3 protein expression; these modifications clearly identified the pilocytic astrocytomas from WHO grade II-IV astrocytic tumors as a distinct biological group. Modifications in the level of S100A6 protein expression enabled a clear distinction to be made between low (WHO grade I and II) and high (WHO grade III and IV) grade astrocytic tumors. Very significant modifications occurred in the level of S100A1 protein expression (and, to a lesser extent, in their of the S100A4 and S100B proteins) in relation to the increasing levels of malignancy. While the S100A5 protein was significantly expressed in all the astrocytic tumors (but without any significant modifications in the levels of malignancy), the S100A2 protein was never expressed in these tumors. These data thus indicate that several S100 proteins play major biological roles in human astrocytic tumors.     

An Analysis of Latch Comparator Offset Due to Load Capacitor Mismatch

This brief analyzes the effect of load capacitor mismatch on the offset of a regenerative latch comparator. Two analytical models are presented and compared with HSpice simulations. Our results indicate that in a typical 0.18-mum CMOS latch, a capacitive imbalance of only 1 fF can lead to offsets of several tens of millivolts