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Application of Instrument Amplifiers to the design of Very High Gain Low Noise Pre-Amplifiers for Audio Signals

Question asked by SuperTrooper on May 14, 2013
Latest reply on May 21, 2013 by krisf

I read the article "Frond End Turns PC Sound Card into High Speed Sampling Oscilloscope" in the Volume 4, 2011 edition of the Analogue Dialogue magazine and would like to know if any Analog Devices engineers are aware of a cost effective device built on Instrument Amplifiers that acts as a low noise high gain pre-amplifier for sound cards.


I am looking for a pre-amplifier that is similar to Instrument Amplifiers in its ability to amplify very low voltages in the range of microvolts to a voltage level much higher than 100mV (typical threshold for detecting signals at the input of sound cards) but which is targeted at audio applications (amplification of the output of a very low noise microphone).


The sound source will be a low noise (14dba) microphone with a sensitivity of (38mV/Pa) which will be powered by a 5V 3.5mm (1/8") audio jack (The pre-amplifier should be able to deliver the 5V supply to the microphone at its input jack). The signals will subsequently be fed into the 3.5mm input of a PC/tablet sound card.


The desired gain is in the region of 100-120dB with variable gain (in stages controlled by the user) and automatic gain control to ensure the sound card input is not overloaded. (Gain should be automatically cut off if the output signal exceeds a given level).


If you are not aware of such a device I would like to know if anyone is aware of a reference design that can accomplish the above requirements or would kindly prove assistance for the development of such a design.


Thanks in advance for your kind consideration.