# MICBias Ground in audio codec

MICBias is the voltage required for microphone to power and record signal at full levels.

What will happen if we ground MICBias, is it means we are disabling microphone.

• what does the data-sheet for that chip say say is connected to the micbias pin. it's likely that grounding it will increase the power consumption of the chip slightly. is MICBIAS connected to other parts of the device, or only to the chip and capacitor? – Jasen Feb 14 '18 at 6:58
• As per the datasheet: " It is the voltage that a device needs and is designed to receive in order to function properly. In the case of microphones, it is the voltage that a microphone is supposed to receive in order to be able to power and record signal at full levels." It is only connected to chip and capacitor – md.jamal Feb 14 '18 at 6:59

Yes, grounding MICBIA will cut off Mic. or at least attenuate greatly.

All electret mics need a bias since they have a common source FET at some current such that Rbias (ext) determines mic source gain and (xIP-xIN)pp max.

Shorting MICBIAs would result in poor mic sensitivity.

You must choose Rbias so expected input level optimizes SNR quality.
Make VMID well above (xIP-xIN)pp to allow for Rbias drop.

Choose VMID for MICBIAs = 2x(0.8)=1.6 x VMID.

Then VMID becomes ADC Vref i.e. maximum input which gives you a few choices of gain from AVDD1.

The datasheet must give more details.

That would be my approach....

• doesn't really say anything about the circuit shown. – Jasen Feb 14 '18 at 6:58
• what ?? my answer or the datasheet? (-1) ...... xIP = LIP< RIP – Tony Stewart Sunnyskyguy EE75 Feb 14 '18 at 12:43