Application Note AN-1798 (pdf 95KB)

Designing with Electro-chemical Sensors
Muna Acosta, Principle Applications Engineer

As early as 1950, electro-chemical sensors were used for oxygen (gas) monitoring; however, with increasing concerns about personal safety, the demand for portable electro-chemical sensors has dramatically increased. Today, electro-chemical sensors are commonly used in portable equipment to detect different toxic gases.

Electro-chemical sensors operate by reacting with monitored gas and producing an electrical current that is linearly proportional to the gas concentration. Older versions of electro-chemical sensors were based on a two-electrode configuration; however, to achieve superior electro-chemical stability, three-electrode systems are now used. The three electrodes are stacked parallel to each other, separated by a thin layer of electrolyte that provides ionic electrical contact between the electrodes.

Application Note AN-1803 (pdf 568KB)

Design Considerations for a Transimpedance Amplifier
Maithil Pachchigar, Applications Engineer

It's challenging to design a good current-to-voltage (transimpedance) converter using a Voltage-Feedback Amplifier (VFA). By definition, a photodiode produces either a current or voltage output from exposure to light. The Transimpedance Amplifier (TIA) is utilized to convert this low-level current to a usable voltage signal and the TIA often needs to be compensated for proper operation. This article explores a simple TIA design using a 345 MHz rail-to-rail output VFA, such as National's LMH6611. The main goal of this article is to offer necessary information for TIA design, discuss TIA compensation and performance results and analyze the noise at the output of the TIA.