Simple op amp plans needed

[2WAYTECH]

Hi, I am new here. I need to build an op amp with a single supply input. I am trying to amplify a signal from 125mVrms to a nominal 1 volt pk-pk. So any help I could get regarding plans or direction for building a low power single supply op amp with a gain factor of about 5 or 6 would be awesome. Thanks.

 

[gvi70000]

what op amp are you using?

 

[2WAYTECH]

I was thinking about using a LF351 or an LM741

 

[crutschow]

For a single supply it's easiest if you use an op amp designed for such use, such as these suggested by Audoguru:

• MC34074 (OnSemi) - V=3/44, GBW=4.5MHz, Bipolar (no R-R), 0.71€
• MC33174 (OnSemi) - V=3/44, GBW=1.8MHz, Bipolar (no R-R), 0.70€
• MC33204 (OnSemi) - V=2/12, GBW=2.2MHz, Bipolar, 0.96€
• TLV2374 (TI) - V=3/16, GBW=3MHz, CMOS, 0.81€
• TLC274 (TI) - V=3/16, GBW=1.7MHz, CMOS, 0.46€
• TLV2464 (TI) - V=2.7/6, GBW=6.4MHz, CMOS, 1.48€
• LM6134 (NSC) - V=2.7/12, GBW=10MHz, Bipolar, 2.82€
• LMC6484 (NSC) - V=3/15, GBW=1.5MHz, CMOS, 2.55€
• MCP604 (Microchip) - V=2.7/6, GBW=2.8MHz, CMOS, 0.78€

Is your signal a normal AC bipolar signal (+/-) centered around ground? If so then you will need to couple the signal through a capacitor with the cap output going to a resistor divider connected the + supply and ground. Two 20kΩ resistors should work. The capacitor needs to be large enough to transfer the lowest signal frequency into a 10kΩ load. For 20Hz this would be 1µF or greater.

Connect the junction of the two resistors and capacitor to the op amp + (non-inverting) input.

For a nominal gain of 5.6, connect a 10kΩ resistor from the - (inverting) input to ground and also connect a 46kΩ resistor from the op amp output to the - input.

The output voltage will have a DC offset of 1/2 the supply voltage. If you need the output referred back to +/- ground level, you will need to add a capacitor at the op amp output.