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AD8220 driving long cables/capacitances differential

Hello everyone,

for my current design I plan to use the IA AD8220 (Gain: ~20dB, frequency: DC-10kHz) to readout a audio piezo transducer. The output signals has to be differential since it's connected to a high resolution diff-adc (24bits). Amplifier/Transducer and ADC are about 1000ft away from each other (twisted pair, awg28)! I expect a cable load capacitance in the range of 30-50nF.

Following single-ended to differential solutions came to my mind:

a) the ad8220 datasheet (p.24, figure 65) suggests the addition of one OP1177 to perform the conversion.

b) using an additional difference amp like the AD8273 in G=4 configuration (AN-1165, p.6) at the IA output

c) using a SSM2142 driver. this only is some sort of "last resort" due to the relativ high supply current (5mA), bulky cases and my experiences in other projects.

Thank you for your advices/other ideas.

  • Hi wildcard96,

    I think the best way to implement your system is to use the last option with some additional. I can say that by using a specialized line drivers and receiver would fit to your requirement. I cannot say that the first two option won't work but to drive and maintain the signal integrity through a long cable could be best with line driver and receiver. Please see the image below. It use SSM2142 line driver and SSM2141/2143 for the receiver. After the receiver, you can add a single ended to differential amplifier that will fit your ADCs requirement. Please let me know if you have any other concern.



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