Figaro TGS5042 Carbon Monoxide Sensor & Op Amp

[sharathb]

In data sheet they have mentioned IC name as AD708 to be used but they have different IC's under its name AD708AQ and AD708BH etc.
which one should i use and many have reported struggles with configuring TGS 5042 CO sensor to get correct measurement, so any suggestions about it,

This'll be the alternate measuring circuit i found on internet which says it prevents polarization as mentioned in data sheet, what is polarization of sensor??
which circuit should i be using?