Various types of basic electronic projects using operational amplifier-based projects are already posted on bestengineeringprojects.com. Now, here is another basic project using an operational amplifier called a microphone amplifier using 741. The circuit microphone amplifier amplifies weak electric signals converted by the microphone to the necessary level.
More other circuits using microphones are posted on bestengineeringprojects.com
- Dynamic Microphone Preamplifier Circuit
- Listening Bug Circuit using op-amp LM386
- DIY Hearing Aid Circuit using 555
- Sound Activated 0-30 Minutes Timer Circuit
- Arduino-Based Automatic Call Answering Machine
- Sound detector circuit using op-amp 741
Circuit description of microphone amplifier using 741
The entire circuit of the microphone amplifier is built around operational amplifier 741. Op-amp 741 can be used in both inverting mode and non-inverting mode according to necessary. Here we use 741 in inverting mode because in inverting mode input impedance is low.
A microphone is a transducer that changes sound energy into an electric signal. The microphone detects sound and changes it into an electric signal which is very weak and needs amplification before being given to the loudspeaker. The output of the microphone is given to pin 2 of IC1 through resistor R3 and capacitor C2 as shown in the circuit diagram. The output is taken from pin 6 of IC1. The value of amplified output is equal to R1/R2 where the value of resistance R1 is set according to the impedance of the microphone. Here we used resistor R4 as a load resistor.
PARTS LIST OF MICROPHONE AMPLIFIER USING OPERATIONAL AMPLIFIER 741
Resistor (all ¼-watt, ± 5% Carbon) |
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R1 – R3 = 1 KΩ R4 – R6 = 10 KΩ R7 = 1 Ω VR1 = 470 KΩ |
Capacitors |
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C1, C4 = 100 µF/12V (Electrolytic Capacitor) C2 = 220 nF (Ceramic Disc) C3 = 100 nF (Ceramic Disc) C5 = 3.9 pF (Ceramic Disc) C6 = 220 nF (Ceramic Disc) |
Semiconductors |
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IC1 = LM 741 (General Purpose operational amplifier) D1 = 1N4007 (Silicon Rectifier Diode) |
i want exact circuit for microphone amplifer using op amp 741 using multisim
Here it is.
Already built it, but how can I know if it works? Am I supoosed to connect the outputs to an oscilloscope? What am I suposed to see?
you may connected it’s output to loudspeaker
You will get amplified audio signal of 53.6 dB and the cutoff frequency of 87 KHz.
Sir are we supposed to connect it to a CRO
The output is connected to either speaker or other amplifier stage (if available).
Thank you sir.
i want to ask. what is the function of C2? why it connected to pin 8 and 1?
thanks
It is used as bypass capacitor.
Where should I construct this circuit? printed circuit board or Veroboard ?
Any where you want.
Generally we use veroboard for testing of circuit and printed circuit for use the device.
sir thank u for the knowledge. but, sir the circuit is not giving the required output sound in the speaker. sir pls tell how can i get the required output.
This circuit is pre-amplifier stage, for proper output you have to add extra amplifier circuit.
could this circuit be readily connected to an audio amplifier ? is there no need for matching?
You can directly connect this circuit output to an audio amplifier without any modification.
Sir , the circuit is not giving the required output? Plz tell me what should I do to get the output.
Please reconnect the entire circuit and check it again you will definitely get your required output.
The output of the above circuit is 53.6 dB and the cutoff frequency 87 KHz.
Sir , can you tell me which type of microphone is used in the circuit?
Here in this prototype, an electret microphone is used.
please give me the working principle of this circuit
The circuit used here is in inverting-mode as we gave the vin (output of microphone) to the inverting terminals.
As op-amp 741 is negative feed-back operational amplifier, so we connect output back to input (- terminal) through series capacitor c5 and resistor R6, which is worked as low pass filter (upto 86 kHz).
What is the value of C6? It is not in your parts list
Thank you for let me know, I had updated the value of capacitor C6
Since R1 = R2, won’t the gain be unity? Also, how can R1 and R2 determine gain? I believe the gain of op amp is the ratio of feedback resistance to the input resistance, isn’t that right? If so, What will happen if R1, R2, and C1 are removed?
we know that for inverting amplifier gain (A) = R2/R1 where R2 is feed back resistor. but in above circuit, the feed back network consist of capacitor with a resistance and a variable resistance. As the circuit is configured in integrator mode the gain would depend upon the feed back network (c5, vr1 and r6) and input resistor r3.
What is the use of VR1,R6,C5
Here, we had used op-amp as integrator circuit and three components are used as feedback network. VR1 give a path to flow bias current where as capacitor with r6 is used as integrator components.
Microphone output is AC and input voltage is DC if it’s combined together means will it affect the circuit?
The DC voltage given to the circuit is just for operating voltage for various semiconductor not as input voltage. The circuit takes input as ac (output of microphone contains frequency and amplitude) from microphone and amplify it and produce output AC signal.
What is the need of pre-amplifier stage. Why we can’t give microphone output to amplifiers
This looks like it is meant to use an electret type microphone?
R5 should be bypassed with a capacitor (1-10u) to block DC supply noise
Sir do you have any physical circuit for our reference for making the circuit Add a picture for reference
Sorry, right now we do not have but in near future we will upload.
what’s the frequency response of this cirucuit?
sir, much voltage gain is obtained here? and also what’s the frequency response of this circuit?
I can’t find the video
Right now there is no making video of making.
Please, I am now working on this project and I have to submit it soon. Can you help me with more explanation and application to the simulation?
All the required details are already posted on the article.
Can you provide the PCB connection for this circuit?
In your description of your circuit diagram, you state the output from the Microphone is given to pin 2 of IC1 via Resistor R1, surly this is a mistake and it should be C2 & R3.
What type of Pot would you recommend for VR1?
Hi
In the comments, you say that the circuit can be connected to a speaker, I connected the output to a 8 ohm 500mW speaker but I don’t hear anything, then you say in another comment that the circuit must be connected to a amplifier.
I would of thought that a very small Speaker connected, something should be heard ?
Should the +ve of the electrec microphone be conneted via a resistor, say 22k to +ve supply ?
Connect the microphone as shown in circuit diagram.