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ifelipeg
06-17-2016, 08:51 PM
I'm developing a soundmeter and i need to construct a pre amp which helps me putting putting one signal from 14 mv to 1050 mv, i already tried with some ops and with transistors, but i need to keep my noise under 700 micro V and the inner noise of my pre amps at the output is around the 10 mv, can someone recomend me a good desing with good gain levels and really low noise at the output.

WMXZ
06-17-2016, 09:06 PM
I'm developing a soundmeter and i need to construct a pre amp which helps me putting putting one signal from 14 mv to 1050 mv, i already tried with some ops and with transistors, but i need to keep my noise under 700 micro V and the inner noise of my pre amps at the output is around the 10 mv, can someone recomend me a s good desing with good gain levels and really low know at the output.
what is the input sensor?

@ifelipeg, if you ask why I ask, read Ben's post that follows

Ben
06-17-2016, 09:42 PM
Choosing the right low noise OP depends on source resistance. For low source resistance, you need low voltage noise. For high source impedance you need low current noise. Limiting the bandwidth also helps to reduce noise. What circuit or part generates the 14mV signal? Is 14mV the peak value or peak-to-peak or rms?

ifelipeg
06-17-2016, 10:12 PM
Hi, Im using an EM173 from primo MIC, @94dB or 1 Pascal the Mic is giving me 14 mV, the Sourse impedance is 680 Ohms

Ben
06-17-2016, 11:42 PM
680 Ohms is low, so you must aim for low voltage noise. If you have symmetrical supply voltages available there is a huge number of op amps to choose from, for example the LT1028 has very very low noise. But your goal of 700ÁV doen't call for such extreme measures. Have you checked the noise on your voltage rails and how much noise the connection between the mic and your amp can pick up? Maybe there is a source of error.

PaulStoffregen
06-22-2016, 12:35 AM
This may be a silly question, but have you asked Primo if they have any recommendations for a preamp to use with their microphone?