A low-power third-order ΔΣ modulator using a single operational amplifier
An architecture for low-power ΔΣ modulators suitable for high-resolution portable sensor systems is presented. The circuit uses a single operational amplifier to achieve a third-order noise shaping. The two-stage op-amp employs a boosting technique that increases by 5 the slew-rate. The circuit, simulated at the transistor level using a conventional 0.18-µm CMOS technology, obtains a peak SNDR of 88 dB over an input signal bandwidth of 100 kHz. The simulated power consumption is 125 µW with a 1.5-V supply voltage. The achieved Figure of Merit (FoM) is 31 fJ/conversion-level.
Third-order ΣΔ modulator with 61-dB SNR and 6-MHz bandwidth consuming 6 mW
This low-power sigma-delta modulator targets the DVB-H requirements and achieves about 10 bit with 6-MHz signal band and a FoM of 0.59 pJ/conversion. The used scheme is a multi-bit third order modulator that, with suitable topological modification, enables using two op-amps and enjoying a swing reduction at the quantizer input. The area of the circuit, fabricated with a 0.18-mum analog CMOS technology, is 0.32 mum2. The nominal supply voltage is 1.8 V and the clock frequency is 96 MHz (OSR = 8). Experimental measurements confirm the behavioral study made accounting for the op-amps limitations.
BIOSYNTHESIS OF DAUNORUBICIN GLYCOSIDES: ANALYSIS WITH BLOCKED MUTANTS
ABSTRACT Daunorubicin (daunomycin; NSC 82151) is an anthracycline antibiotic that is useful in the treatment of human leukemias. Several Streptomyces species accumulate higher glycosides of daunorubicin, which can be converted to daunorubicin by simple hydrolysis. We isolated a number of mutants of a daunorubicin glycoside-producing streptomycete, and found that some were deficient in accumulation of daunorubicin glycosides. One such mutant accumulated no detectable anthracyclines, while other mutants accumulated anthracyclines or aglycones that have not been reported before or have been described as co-metabolites of daunorubicin glycosides. Some of these anthracyclines and aglycones were purified and used as substrates in bioconversion experiments with various mutants. The results allowed us to construct a proposed pathway for the biosynthesis of daunorubicin glycosides by this streptomycete. KEYWORDS Anthracycline; daunorubicin; biosynthesis; blocked mutants; biotransformation.