The circuit attached is an inverting amplifier with variable gains. The CT measures 60 Hz currents from 0 to 30A. It has high sensitivity since it's used to measure low ground fault currents. I added a DC bias to the AC signal as shown for the ADC processing. I have the following questions:
1. As I'm using an IC (LM4041) for the voltage reference, would I need to buffer it with the op amp?
2. I added a coupling cap C3, but not sure how it would affect my signal. It's a high pass with a cut off frequency of ~20Hz. C19 forms a low pass filter. Should I leave C3 for this application?
3. If op amps are cheap or low quality, would the offset voltage affect significantly?
4. If for some reason the primary current exceeds 30A, would diodes across the CT help clamp any over voltage? I usually see diodes used when the signal swings around zero, but in this case it swings around 1.65V (3.3/2).
Any suggestion is appreciated.
1. As I'm using an IC (LM4041) for the voltage reference, would I need to buffer it with the op amp?
2. I added a coupling cap C3, but not sure how it would affect my signal. It's a high pass with a cut off frequency of ~20Hz. C19 forms a low pass filter. Should I leave C3 for this application?
3. If op amps are cheap or low quality, would the offset voltage affect significantly?
4. If for some reason the primary current exceeds 30A, would diodes across the CT help clamp any over voltage? I usually see diodes used when the signal swings around zero, but in this case it swings around 1.65V (3.3/2).
Any suggestion is appreciated.
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