I keep seeing this difference amplifier setup:
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/opampvar6.html
But never this one (image attached). It's basically a modified non-inverting amplifier where the reference is a voltage other than ground. Is there a reason for never seeing this circuit and always the first circuit? It seems to me both would work...why does it seem one is usually spoke off and the other one isn't? I need more of a "voltage de-biaser+amplifier" but I'm don't think that's any different from a difference amplifier where one input stays constant.
EDIT: It might be important for you to know that I am using a resistive dividier buffered with an op-amp to provide the bias voltage to the - terminal of the op amp. It's to detect motor Back EMF. The back EMF signal is biased at +V/2 (and the back EMF is always positive so the reading is always >(+V/2). WHat I want to do is remove this bias and then amplify it so I am only amplifying the back EMF and not the bias.
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/opampvar6.html
But never this one (image attached). It's basically a modified non-inverting amplifier where the reference is a voltage other than ground. Is there a reason for never seeing this circuit and always the first circuit? It seems to me both would work...why does it seem one is usually spoke off and the other one isn't? I need more of a "voltage de-biaser+amplifier" but I'm don't think that's any different from a difference amplifier where one input stays constant.
EDIT: It might be important for you to know that I am using a resistive dividier buffered with an op-amp to provide the bias voltage to the - terminal of the op amp. It's to detect motor Back EMF. The back EMF signal is biased at +V/2 (and the back EMF is always positive so the reading is always >(+V/2). WHat I want to do is remove this bias and then amplify it so I am only amplifying the back EMF and not the bias.
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