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Design >> Analog Design >> Differential noise at the input of Differential Amplifier
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Message started by Hasliadi on Jan 14^th, 2015, 11:29pm

Title: Differential noise at the input of Differential Amplifier
Post by Hasliadi on Jan 14^th, 2015, 11:29pm

Hai! Good day everyone.

I am freshman of analog design and currently develop the interfacing circuit for electrochemical sensor. In my design, it produces a dual output signal (VOA & VOB) from a single input. Currently I am investigate the noise performance by applying the transient noise at the input of my design and differentiate between the outputs. the simple method to differentiate both of output signal included noise is use the differential amplifier since the diff_amp has ability to reject any common mode noise.

Unfortunately the output of diff_amp become a noisy(VOC). I notice that, it is because the inputs of diff_amp has different amplitude noise (see attachment). I am not sure whether my way to analysis the noise performance is correct or not? is it possible, the different mode noise exists between the input of diff_amp? if Yes, is there any method to reject these noises without using a filter?

Thanks a lot

Best regard
adie

Title: Re: Differential noise at the input of Differential Amplifier
Post by loose-electron on Jan 19^th, 2015, 1:19pm

OK, is the horizontal scale in the milli seconds or Mega seconds?

Either way you need to limit the bandwidth of your system to that only of the signal of interest.

After that, if it is extremely slow signal I would suggest ADC followed by digital averaging to reduce BW further and average out the noise.

Also, the noise can be further lowered by reducing the impedance of these sytems to reduce the thermal noise.

Other techniques are possible as well.

http://electronicdesign.com/analog/noise-reduction-crucial-mixed-signal-asic-design-success

http://electronicdesign.com/analog/noise-reduction-crucial-mixed-signal-asic-design-success-part-ii

the above are useful as well if it is an interference noise question.