output noise of AD8421ARZ

Hi DPFATE_DP ,

Can you share your input and output scope measurement?

Best regards,

Franz

Output is just like the picture above. but it is the result of gain = 4000. No input signal. I connect the vin+ with vin- and you can refer to the circuit of my question.

Thanks! 

Output is just like the picture above. but it is the result of gain = 4000. No input signal. I connect the vin+ with vin- and you can refer to the circuit of my question.

Thanks! 

Hi DPFATE_DP,

Could you check the noise on your power supply as well as your vref?

Best regards,
Franz

Hi Franz,

I am so sorry. My previous description is wrong. In fact, I use two AD8421 to get two stage of amplifier. the Gain of first  stage is 80 and second stage is 50. The test circuit of first stage is  shown as the picture in my question and its output is connected with the VIN+ of the second stage. And the VIN- of the second stage  is connected with GND. I found that approximately 10mv noise is generated on the power supply pin.

Hi DPFATE_DP,

Since there is also a 10mV noise on your power supply pin, the noise may come from your power ICs. You may check your power management for noise sources. AD8421 needs a stable DC voltage as the noise can adversely affect performance.

You may place a 0.1uf  decoupling capacitor as close as possible to each supply pin.

I hope this helps.

Best regards,
Franz

Hi Franz,

Could you give me some advice about which power ICs I should select ?

Best regards,

DPFATE_DP 

Hi DPFATE_DP,

You may want to consider ADR435 which has a very low-noise output. However, please consider that ADR435 is a voltage reference IC with only 30mA of output current. This might not be sufficient if you will use this for your other ICs.

Kindly visit our power management forum to inquire about a proper power management IC for your system.

I hope this helps.

Best regards,
Franz