Monday, January 30, 2012

Designing a Low-Power Toxic Gas Detector

Safety first! Many industrial processes involve toxic compounds, including chlorine, phosphine, arsine, and hydrogen cyanide, so it is important to know when dangerous concentrations exist.This article describes a portable carbon monoxide detector using an electrochemical sensor. CO is relatively safe to handle, but it is still lethal, so use extreme care and appropriate ventilation when testing the circuit described here.

Robust Amplifiers Provide Integrated Overvoltage Protection

Faulty performance or damage can occur when an op amp’s input voltage exceeds the specified input-voltage range. This article discusses some common causes and effects of overvoltage conditions, how cumbersome overvoltage protection can be added to an unprotected amplifier, and how the integrated overvoltage protection of newer amplifiers provides a compact, robust, cost-effective solution.

Monday, January 09, 2012

Efficient FSK/PSK Modulator Uses Multichannel DDS to Switch at Zero Crossings

This article describes how two synchronized DDS channels can implement a zero-crossing FSK or PSK modulator. In phase-coherent radar systems, zero-crossing switching reduces the amount of post processing needed for target signature recognition; and zero-crossing switching reduces PSK spectral splatter. Here, the AD9958 two-channel complete DDS is used to switch at the zero crossing.

DDS Devices Generate High-Purity Waveforms Simply, Efficiently, and Flexibly

Direct digital synthesis (DDS) technology is used to generate and modify high-quality waveforms in a broad range of applications in such diverse fields as communications, defense, medicine, industry, and instrumentation. This article provides an overview of the technology, describes its strengths and limitations, looks at some application examples, and showcases some significant new products.