input a sine signal to the circuit, the frenquncy and amplitude do not change.
the output always changes at a low frequncy
could you help to explain that? thanks a lot.
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input a sine signal to the circuit, the frenquncy and amplitude do not change.
the output always changes at a low frequncy
could you help to explain that? thanks a lot.
Antony,
Is the problem only with the op amp circuitry, U7A?
I'm sorry but we do not understand the problem. Please provide a more complete description of the problem. Please provide circuit values for the components connected to U7A. Please provide information on the power supply voltage and V_COM_REF voltage.
Regards, Bruce.
I mean the RMS is not stable,it swings a small amplitude,and this make the precision bad.
Antony,
For the resistor values you have indicated, the amplifier differential gain is very low-- 0.000824 V/V. It would require more than 1000V differential input to create a 1V output from the amplifier. Is this what you intended?
Regards, Bruce.
Antony,
You will need to provide more specific information on the performance you are getting. Describe what you mean by "unstable." What is your input voltage? What output voltage are you getting. Have you looked at the output with an oscilloscope? Can you provide an ocillloscope waveform of the output that defines this behavior?
Sorry, but I can't help without a clear understanding of the problem.
Regards, Bruce.