need some assistant on the op-amp circuit attached in the thread.

[scream_er]

Hello, people. Regarding the attached circuit, can someone answer to some questions about it.

• I would like to know why a non-inverting input op-amp is used and why not an inverting op-amp?
• Why do we need a feedback loop?
• Also why is that the gain is determined by the ratio of the two resistors forming the divider bridge at the output of the OpAmp?
  
  The link for the circuit (**broken link removed**) and please be kind, I am a newbie on electronics
  
  **broken link removed**

 

[kak111]

In basic op-amp circuits, the input resistance is much higher for non inverting configuration,
so it won't load signal sources which have relatively high output impedance.

Second reason is simply, that using a non-inverting configuration allows you to seperately alter gain and input impedance.

why is that the gain is determined by the ratio of the two resistors forming the divider

Here is good reading about op-amps, i suggest you to find the answer(s) there....

HANDBOOK OF OPERATIONAL APPLICATIONS :
https://www.ti.com/lit/an/sboa092a/sboa092a.pdf

If you want to explore more deeply....

OP AMPS FOR EVERYONE
Design Reference
**broken link removed**

 

[juz_ad]

A few suggestions...

[*]I would like to know why a non-inverting input op-amp is used and why not an inverting op-amp?

There's two reasons I can think of. 1) It gives you a non-inverting output from a single op-amp i.e. you don't have to have an inverting gain stage and then an (un)inverting stage. 2) Generally, I see more non-inverting configurations in single supply circuits i.e. 0 to 5V, 9V or 12V DC as opposed to +/-12V or +/-15V DC. At a guess, I would suggest that the demands of small, single-supply circuits are generally simpler and the potential problems you might have with using a non-inverting configuration just aren't an issue. For single-supply circuits I always tried to use non-inverting when I could, for dual-supply - I try to stick to inverting.

[*]Why do we need a feedback loop?

The feedback loop on IC2A provides gain. Normally the gain is set by the ratio of the input resistor and the feedback resistor i.e. 10K and 10K is unity gain (no gain) and 1K / 10K is 10x gain. The input resistor has been omitted here, not sure why - possibly because the output of the electret is so small?

The electret output signal is biased to virtual ground (+2.5V) by the voltage divider formed by R3 and R4 - that makes sense as it's an AC signal. I'm not sure what purpose R5 and R6 are serving.

[*]Also why is that the gain is determined by the ratio of the two resistors forming the divider bridge at the output of the OpAmp?

I believe, in this configuration, R1 sets the gain and R2 sets the impedance of the output at 1K - but it's not a config I have seen before. I'm not sure what purpose C3 serves in this config... as an AC coupled output (which would make sense) R2 and C3 would be run in series with each other.

please be kind, I am a newbie on electronics

I hope these answers help - but please check them for yourself.

 

[scream_er]

What I want to achieve is that, I want to connect the output from microphone to Microprocessor (arduino) and to speaker. So when I scream or whisper the microprocessor will detect the voltage and print out for me on the computer. And if the voltage is higher than a certain value it will on the speaker and output the voice. So, to achieve this I am using an electret microphone, a speaker with 8ohms and 0.5W and arduino Uno. I would like to know how and what I I should do to achieve this?