Hello
I want to use a low noise instrumentation amplifier to detect the very small audio signals (in the order of some micro or nanovolts) of an electret microphone before feeding the signal into a digital operational amplifier. It is for a photoacoustic experiment to detect trace amounts of CO2, so low noise, a sufficient gain to feed the signal into the lock in and a wide dynamic range is important for me. To me, INA163/Ina217 was suggested (or is another one better?), and I have looked at the circuit of the professional microphone amplifier. However, I do not really understand the circuit and therefore, it it difficult for me to adjust it to my needs... I do not need a phantom power of +48V, can I just use 2 power supplies instead of 3 like you and use R1 to place 2 voltage at the microphone? It would look like the circuit of the person who has designed the circuit for the panasonic electret microphone in this forum. Or is there a problem with the incorrect current flowing into the opamp power supply pin when I use one power supply for both? I Can I choose a smaller Vpps without changing the values of the resistors and capacitors in the circtuit? Ofcourse, I need to change the value of R1 then, but otherwise?I Ofcourse, I want the minimal power consumption, but only if no deterioration of the system is the consequence! Now, in my application, I am only interested in the signal at 1000 Hz, so could I I place a bandpass filter somewhere in the circuit? Or would this increase the noise? Or would you consider this as not necessary as I use a lock in amplifier anyway afterwards? And what about the output? Can I just connect the output pin on my breadboard to the lock in via a bnc cable, or do I need to place additional things like capacitors and resistors? I really just work with a breadboard/europlatine where I stick/solder the microphone, the capacitors and resistors onto. The outputpin is also directly fed into the lock-in with a BNC cable. You see, I try to keep it simple as I am a chemist with no experience with electronics, but I still need a good amplifier to do the first experiments!
The microphones I use: EM172 or EM173 and EM172 from Primo Microphones. Here is one more question: although EM172 is more sensitive, it has a smaller dynamic range. What would you think is more important in my case/fits better here?
The lock in is the MFLI from Zurich Instruments.
I hope you can help me out here! Thank you already in advance, Patrizia
