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Low voltage, power and noise microphone amplifier help
Low voltage, power and noise microphone amplifier help
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Old 8th February 2018, 06:35 PM   #1
Vuokko is offline Vuokko  Finland
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Question Low voltage, power and noise microphone amplifier help

Hello!

I'm designing microphone amplifier for my portable recorder. The recorder line in but I want to plug microphone to it and this is giving me some headache.

My idea is to select some mic for the purpose and plug it into the XLR port and connect the 3.5mm plug to the recorder.

Getting the +60dB amplification from any opamp is easy. Also making the system low noise is relative easy and designing microphone amplifier is easy. Just copy circuit from THAT corporation application note.

Unfortunately I don't want to design two sided power supply and I can't afford the power which is needed with the traditional amplifiers. Something like 5 volts single sided power supply and adjustable phantom voltage should be enough to keep the dongle running some time and the it stays in portable size. 120Ah lead acid battery bolted to small circuit isn't my idea of portable.

So has someone designed this kind of stuff and know good chips to use or has seen good application notes? Also good other good ideas are welcome.

I'm quite much in the beginning and I have just simulated some opamps to check the noise and power consumption. I'm looking shortcut here so that I don't have to try all possible combinations.
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Old 8th February 2018, 07:30 PM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by Vuokko View Post
So has someone designed this kind of stuff and know good chips to use or has seen good application notes?
Check out the TLV2772CDR, worked well for me. Bear in mind the loss of headroom
when using a 5V single supply, a factor of 6 lower (-15dB) than +/-15V supplies.
TLV2772 Dual 2.7-V High Slew Rate Rail-To-Rail Output Operational Amplifier | TI.com

Last edited by rayma; 8th February 2018 at 07:42 PM.
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Old 8th February 2018, 08:05 PM   #3
JMFahey is offline JMFahey  Argentina
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Quote:
Getting the +60dB amplification from any opamp is easy.
Well, actually itīs NOT.

And ... 60dB amplification?
Do you have any idea what that means?
You want to record people's thoughts?
Or speakers 1/4 mile away?
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Old 8th February 2018, 10:46 PM   #4
voltwide is offline voltwide  Ireland
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Originally Posted by JMFahey View Post
Well, actually itīs NOT.

And ... 60dB amplification?
Do you have any idea what that means?
You want to record people's thoughts?
Or speakers 1/4 mile away?
There may be acoustic events far below the 120dB A sound levels of rock concerts where 60 dB gain makes sense. Old school analog mixing consoles provide similar gain at max gain setting. Anyway, this gain requires 2 OPA stages for acceptable performance.
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Old 9th February 2018, 12:16 AM   #5
jackinnj is offline jackinnj  United States
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Low voltage, power and noise microphone amplifier help
See Scott Wurcer's design -- very creative indeed. My version of the G = 1000 low noise measurement amp (for Ikoflexer).

The optocoupler is used to bias a JFET -- voila.

There are some of these optocoupler/gate bias devices which could provide adequate bias for an electret.
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