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I am trying to measure the output voltage of a full H-bridge. I will post an image of the circuit that I am going to use. The design of the H-bridge is a bit more complex in reality but it is only necessary to know the voltage measurement circuit in the output:

enter image description here

(R1 = R2 = 2M, sorry)

I use a symmetrical power supply on OP1 since the output will be +1 when Vab = 24V and -1 when Vab = -24V. I want to shift the output voltage of OP1 to get an always positive signal (since I will be using a uC that has as Vanalog = 3.3V and GNDA = 0V) so I thought of adding the output voltage of OP1 with 1.65V.

Should I use a symmetrical power supply for OP2 or can I use a simple power supply for this opamp?

If anyone has an opinion about my circuit or thinks that there is a more efficient and elegant way to do it (I think that there is) they would help me if they write it in the comments.

JRE
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WalterPH
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  • How accurate do you need the measurements and how fast/often will you need them? – jonathanjo Mar 29 '23 at 16:18
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    do you really need PWM control on all four H-bridge switches? – jsotola Mar 29 '23 at 16:58
  • Mandatory read on 741: https://electronics.stackexchange.com/questions/304521/reasons-not-to-use-a-741-op-amp – winny Mar 29 '23 at 17:26
  • Responding to all the comments: an error of +/- 0.2V is enough and the frequency of the PWM is 2.5 kHz and it samples the voltage data approximately every 5ms; Yes, I need the PWM on the four mosfets since I use a 2-quadrant control and I switch the two mosfets of a half bridge and in the other half bridge the high mosfet is off and the low mosfet is on; I wasn't planning on using a 741... – WalterPH Mar 29 '23 at 17:59

1 Answers1

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One good OpAmp alone will do this. There are calibrated instumentation amplifiers available, that include all 5 resistors with small tolerances for typical gain values.

R3 parallel to R4 must be equal to R5.

schematic

simulate this circuit – Schematic created using CircuitLab

Jens
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