AMC3301: Input locks up when powering up the amplifier

Klemen Skorjanc

Part Number: AMC3301

Hi,

we used the AMC3301 to read low voltage source(5mV to 50mV) (chemical reaction sensor), but the input of the amplifier has to low impedance and our voltage source collapsed. Now we added a op amp (gain of 1) as a voltage buffer in front of AMC3301 input and with a separate power supply. When we connect everything up and do not power the AMC3301, we measure 5 to 50mV on the INP and INN of the amplifier. But once the AMC3301 is powered up (3.1V) the input locks to 87mV and doesn't move either way.

What could cause this?

over 4 years ago

0 Klemen Skorjanc over 4 years ago

Prodigy 10 points

P.S. If we attach a 1.5V AA battery via trimmer to INN and INP the it works, so we assume the problem is that are OP amp doesn't provide enough power (current) to the AMC3301, so how much do we need to amplify the input signal (current)?

0 Tom Hendrick over 4 years ago in reply to Klemen Skorjanc

TI__Guru**** 182761 points

Hi Klemen!

Welcome to our e2e forum! Can you provide a drawing that shows how you have the external amplifier/buffer connected ahead of the AMC3301? How is the power applied, where is it referenced, and how do you have the trim pots connected?

+1 Klemen Skorjanc over 4 years ago in reply to Tom Hendrick

Prodigy 10 points

Hi, we managed to get it working by changing the op-amp at the input stage with a stronger one. Below is diagram of a working circuit.

IC6 = AMC3301

U2 = AD8541AR

0 Tom Hendrick over 4 years ago in reply to Klemen Skorjanc

TI__Guru**** 182761 points

Great news! Thank you for letting us know!

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AMC3301: Input locks up when powering up the amplifier