Amplifying signals from Piezo strip TE 10184000-01

Question

We are designing a device which would amplify the signals from a piezo strip TE 10184000-01. 
 Earlier amplifier used was ADA4051-2 with average results to give the signals in the frequency band range of 0.2 to 05 Hz and 1 to 3 Hz. 
 Will the one out of the following two will be better? 
 LTC2067 , 
 AD8629 
 We need minimum external components for the filtering of 50/60Hz and the above mentioned filtering of frequency signals.

MarkThoren · Accepted Answer

Hi Plawat, 
 It is likely that none are appropriate. These are autozero amplifiers, which in spite of relatively high input impedance, can have transient currents from the autozero circuitry that can manifest as elevated noise when the input impedance is high. 
 There is no offset specified for this sensor, and DC offset is not important in these applications, so you don't need autozero. 
 From the datasheet, the most important amplifier spec looks like input impedance: 
 " To obtain a response to 0.1 Hz (-3dB point) with a simple voltage-mode circuit, an input resistance of 220M is required. If only heart rate is required (and not respiratory rate), then a lower limiting frequency in the range 1 &ndash; 3 Hz may be sufficient. " 
 So you will need a very low bias current amplifier, ideally located as close to the sensor as possible. If it is located remotely, you will need to use low-leakage wiring (Teflon or similar). 
 Moving to the op-amp forum as well, since this is a component-level question. 
 -Mark)

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