Op Amps for Everyone, by Bruce Carter and Ron Mancini from Texas Instruments.

op amps for everyone (Texas Instrument).pdf

op amps for everyone third edition 2009 (Texas Instrument).pdf

Op-amp application notes from National Semiconductor,

An applications guide for op-amps.pdf

Single rail op-amp design from Texas Instruments

single power supply design.pdf

Capacitor for Signal Filtering

Capacitances required to attenuate or suppress signal of certain frequency. Please note that this formula and the table presented on the right is an approximation for filtering noise from a DC signal.

Xc = 1 / (2π f C)

C = 1 / (2π f Xc )

where Xc is the reactance of the capacitor. Xc of 1.0 for the capacitor (open circuit) is possible with lower fequency signal or lower capacitance. To attenuate the AC signal of a particular frequency, Xc has to be low with the correct capacitance implemented.

Example:

To attenuate a 50Hz signal by 10 times.

C = 1 / (2π x 50Hz x 1/10) = 31,830uF

This means that to attenuate the 50Hz component by 10 times requires about 33,000uF capacitor connected from the signal to the ground line. This capacitor will filter any frequncy >50Hz on the line.

The table on the right is a simplified guide, which recommend the capacitance to use as a low pass filter for attenuating a particular frequency.

Max frequency for capacitor (taken from "Op Amps for Everyone")