Hardware -- The frontend's TSV634 opamps

A project log for Heartbeat Logger

A portable device that logs a snippet of your heart at the push of a button.

Ole Andreas UtstumoOle Andreas Utstumo 01/25/2016 at 15:320 Comments

The analogue front end requires four op amps to operate. I chose ST Microelectronic's TSV634 for the first revision.

A quad pack of opamps. Taken from ST Microelectronic's TSV63x datasheet.

Some of the op amps features are:

INA321’s datasheet recommends a rather expensive set of opamps. A cheaper op amp from ST Microelectronics was deemed sufficient. As with the in amp, the key feature is the rail-to-rail input and output, operation down to 1.5 V and also its gain bandwith product. The op amp will be required to amplify the signal from the in amp by G = 62 at 256 Hz. The gain bandwith product required is:

GBW P = G f = 62256 Hz = 15.9 kHz.

Which compared to the specced 880 kHz is more than sufficient.