LMV358A-Q1: How to design microphone signal circuit with LMV358

Elec Cheng

Part Number: LMV358A-Q1
Other Parts Discussed in Thread: LMV358

Hi Expert,

Our customer wants to use LMV358 for sampling and augmenting microphone output signal to estimate how load the voice is. Do you have a reference design? More generally, do you have any material about how to design circuit to amplifier microphone signal, such as preamplifier function? Any thing related will be highly appreciated.

Thanks,

Elec Cheng

over 2 years ago

0 Jerry Madalvanos over 2 years ago

TI__Mastermind 22301 points

Elec,

We have several helpful resources in the Analog Engineer's Circuit Cookbook. There are two microphone preamp circuits that I have linked below directly.

https://www.ti.com/lit/an/sboa290/sboa290.pdf

https://www.ti.com/lit/an/sboa291/sboa291.pdf

Best,
Jerry

0 Elec Cheng over 2 years ago in reply to Jerry Madalvanos

TI__Expert 7055 points

Hi Jerry,

Thanks for your recommendation. But I don't understand:

1. why signal gain is -4dB, which means signal becomes smaller. But my goal is to amplifier.

2. the same as question 1, why input signal is even larger than output signal. I assume microphone signal is small and we need to amplifier it.

Thanks

Elec Cheng

0 Jerry Madalvanos over 2 years ago in reply to Elec Cheng

TI__Mastermind 22301 points

Hey Elec,

The explanation of the negative gain is in the system requirements at the top. The input pressure max is 100dB SPL, the output voltage max is 1.228Vrms. So in this case you will need negative gain.

If you go through the steps but substitute your desired values for your system, you can adjust the values to yield a positive gain.

Best,
Jerry

0 Elec Cheng over 2 years ago in reply to Jerry Madalvanos

TI__Expert 7055 points

Hi Eric,

Our customer says the output signal of microphone is differential. But I rarely see this kind of microphone. Do you have any idea? Also, do you have reference design for differential input pre-amplifier ?

Thanks

Elec Cheng

0 Caro Walter over 2 years ago in reply to Elec Cheng

TI__Genius 17447 points

Hello Elec,

I was able to find the following resource: https://www.ti.com/lit/pdf/snoa586
See section 4 "Transformerless Microphone Preamplifiers"

All the best,
Carolina

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LMV358A-Q1: How to design microphone signal circuit with LMV358