| Electronics > Beginners |
| 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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