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Would You Expect this Op-Amp to Amplify Small Voltages?

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deepsatchel said:
Hey, thanks for the info godfreyl! As you suggested I measured the resistor leg to leg; I see a voltage drop of 0.0mV. Does this mean perhaps that for some reason no current is being drawn into the input?
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There must be some small input current. The resulting voltage drop may be too small for your meter to read.

In any event, the point is it's so small it's not worth worrying about. Even if there was half a volt of DC offset the circuit would still work fine, since the input and output are AC-coupled with capacitors.
 

My meter is supposedly sensitive down to 0.1 mV. I was trying to check if that event was actually taking place as a confirmation that the opamp is doing what it should.

By the way, I am just getting started with these opamp amplifiers, so my thinking here may be off-course. I was reviewing the circuit we've come up with and now I'm thinking that this should be the result:

3053830000_1388974528.png


In other words, if we're amplifying the signal on the opamp's noninverting input, shouldn't the DC component get amplified as well as the noise?
 

If you leave out the 10uF capacitor and connect the bottom of the 2.2K resistor directly to ground, then the amplifier would amplify the DC as well.

However, as is, the 10uF capacitor in conjunction with the 2.2K resistor causes the gain to roll off below about 7Hz. The DC gain is unity so the output voltage should be about 4.5V.
 
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