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I have made a single supply non inverting amplifier. The supply voltage given is 5 V. The schematic is shown. Schematic Now the problem is I am not able to generate 2.5 V accurately which is affecting amplification. The 10 K resistor connected to inverting terminal has to connected to 2.5 V. A resistor divider with opamp buffer is not able to generate 2.5 V accurately.

Is there any other approach to amplify signals about half the supply voltage in single supply circuits?

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  • \$\begingroup\$ Show the full circuit including what the 2.5V point connects to. Nobody here is a mind reader. \$\endgroup\$ – Andy aka Jun 3 '16 at 10:48
  • \$\begingroup\$ @Andy aka - The circuit giving 2.5 V is added. \$\endgroup\$ – spider Jun 3 '16 at 11:06
  • \$\begingroup\$ There are excellent resources around to help you understand: I suggest reading this first: ti.com/lit/an/sloa030a/sloa030a.pdf \$\endgroup\$ – Peter Smith Jun 3 '16 at 13:28
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OK, you have a gain of 50 and any difference between the voltage divider (R6 and R7) that feeds U2 and the voltage divider (R3 and R4) that feeds U1 will be amplified by 50 and produce the error.

FIX: -

Get rid of R4 and R3 and connect R5 directly to the output of U2. Also put C2 across R7 to reduce noise.

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  • \$\begingroup\$ I made the changes you suggested. I am using Tsv914 opamp. The amplification obtained was only 3 compared to the desired value of 50.The offset is also incorrect as it is around 3.5 V. \$\endgroup\$ – spider Jun 3 '16 at 12:21
  • \$\begingroup\$ The op-amp seems OK but what input frequency and amplitude did you use? You could also try making R6=R7=100 kohm. I wouldn't expect an error of anything more than 150 mV from the mid-rail - lower the values as said and measure again - also measure directly at the junction of R6 and R7. \$\endgroup\$ – Andy aka Jun 3 '16 at 13:25
  • \$\begingroup\$ I used a frequency of 200Hz and checked with amplitude ranging from 0.01 to 0.05 V. I also changed R6 and R7 to 100k ohm. Even then amplification was not achieved \$\endgroup\$ – spider Jun 3 '16 at 15:24

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