--0__=85256A9B004F28E38f9e8a93df938690918c85256A9B004F28E3 Content-type: text/plain; charset=us-ascii The comparator action of an op amp is based on open loop gain, and stability can become an issue. If you are merely trying to see which is larger, a comparator is a much better choice. If you need to see the difference between the two signals, a differential amplifier is a straightforward way to go. A differential amp can be constructed from 4 resistors and an opamp... relatively simple. Scott F. Touchton Bernard Tyers cc: Sent by: pic Subject: [EE] microcontrolle r discussion list 08/01/01 10:20 AM Please respond to pic microcontrolle r discussion list Hi all, first post. I am trying to use a CA3140E op-amp as a comparator. The two inputs are chemical sensors. The difference voltage between them can range between 400mV, to 50mV (100% concentration to 0% concentration). I remember reading somewhere in a text book, that if V1-V2 is greater than (I think) 100uV the op-amp will go into saturation. Can anyone a) clarify this for me, or b)suggest a better way to measure the difference voltage. Component count is a factor, as is power consumption. (I want my cake and eat it too!) TIA -- rgrds, Bernard -- Bernard Tyers*Dept. of Physical Sciences*Dublin City University*P:01.7005273*L:N117*W:frank.physics.dcu.ie/~bty -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. 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