Hello--
I'm working with an experimental acoustics sensor which will produce voltages ranging between 0.5 microvolt (minimum) and 5 V (peak to peak). What is the best way to digitize this signal? At first blush, it appears that a 24-bit ADC would work quite well for this type of application, since (5V)/(2^24) = 3E-7 Volts. However, would it be better to do the following?
(1) Convert the voltage signal into a current using a transconductance amplifier.
(2) Use a logarithmic amp to find the logarithm of the current. The AD8304 from Analog Devices is a 160dB (100 pA to 10 mA)) logarithmic amp used as a photo-diode detector:
(3) Digitize the voltage output of the AD8304 log amp using an ADC.
BUT how do I determine the number of bits of my ADC? The logarithmic amp will take the logarithm of the signal, but how do I choose the number of bits of the ADC so that I can adequately measure the range of voltages?
OR is it best to simply use a 24-bit ADC?
Nicholas