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I am using YHDC (SCT013) split-core current transformer (100A:50mA) for sensing 3-phase AC. I have connected a 33-ohm burden resistor to the current transformer and with the voltage divider circuit, I am able to get approximately 1-volt output from the current transformer with an offset of 2.5 volts.

The current transformer and voltage divider circuit is as follows,

schematic

simulate this circuit – Schematic created using CircuitLab

My final goal is to feed this output to the NAND, but for NAND the gate minimum voltage must be higher than 3.5 volts. I tried using UA741CN Op-Amp to amplify current transformer output, but I am unable to amplify the voltage.

How do I amplify the voltage from a current transformer?

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  • 2
    \$\begingroup\$ How are you getting an output centered around 2.5V? this is not clear in your schematic. Where were you connecting the op amp? \$\endgroup\$ – Voltage Spike Sep 24 at 15:42
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    \$\begingroup\$ You're trying to measure the voltage across your burden resistor, but you've only connected to it at one point. That'll never work. Are you certain that you don't have one side of the burden resistor grounded? Show us what circuit you attempted with the 741 opamp, and in particular, show us how you powered it. \$\endgroup\$ – brhans Sep 24 at 16:34
  • \$\begingroup\$ Sorry, there was a mistake in the voltage divider circuit. I am connecting Op-Amp to one end of the burden resistor. \$\endgroup\$ – sunil patil Sep 25 at 16:59
  • \$\begingroup\$ I have tried with different R4 and R5 resistance values (R4 >R5) in the amplifier circuit. For V+ and V- I tried with different voltage levels using the bench power supply. \$\endgroup\$ – sunil patil Sep 26 at 14:12
  • \$\begingroup\$ I strongly recommend not using a 741. It has a number of major problems, being a very old design, but most importantly here is that it needs a minimum 10V (equivalently ±5V) supply to operate properly. It's unlikely you'll have such a supply available in your device, but even if you do, there are plenty of other reasons not to use it. \$\endgroup\$ – Hearth Sep 26 at 15:56

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