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What did I miscalculated ??

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GigaJoe:

Fraction of schematic .... I didn't work with OP07, but OK with MC34071 
I'm guessing R6+R7  too high?   What exactly in opamp datasheet i need to look at , and calculate

GigaJoe:
"Input voltage range." -- How so ?

I'm basically amplifying 200mV. The symptoms was:  opamp wasn't able to balance , so positive has 200mV, and negative  input around +450mV.  so the output was around 3.5V I did try couples old opamp, only MC, and TL081 works.

I assumed the current wasn't enough due to high R6 + R7 ...

MarkF:
The OP07 op-amp is not single supply.  You will not be able to get that close to the negative rail (ground in your case).  The input voltage range would need to be a couple volts away from the power rails.  While the MC34071 is single supply.

Your circuit needs a single supply or rail-to-rail op-amp to work correctly.  Give the OP07 a negative voltage and test it again.

boB:
Well, not sure what you're expecting exactly but looks like the DC voltage output of the op amp is approximately correct.

Gain should be approximately 15 with 70K/5K + 1 and 0.193V DC in and 2.9V DC output.

AC component is almost nothing so the frequencies around 12 kHz are probably meaningless here.

boB

GigaJoe:
Wait wait,   where you found  RR operational mode ?????
200mV  * to coeff  ==  up to 2.9 ??? . And it single rail ,  +12V 

Ahh .. get it: AC - are simulator's  nuances, so we looking only to DC ,  no any AC  floating around at all ;  don't look at , only DC ; that all ....


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