Operational Amplifier Tutorial & super microphone circuit

[td0034]

@Chryseus8086 explain how please...

for these purposes the video is perfect. no ones gonna build a recording studio with this info but thats not the point is it. stop being so cynical and go punch a wall rather than troll your life away on youtube.

[TheSpaceApache]

I dislike improper use of the word "awesome." But dude you so awesome, your tutorials are genius.

[TheJennetteFan]

Hey can i use +6v and -6v insted of +9v and -9volts

[Afrotechmods]

@TheJennetteFan That should be fine

[PlayHiFi]

Ohh man this is the most hilarious electronics course I've taken so far.

I LOL'd so hard.

Thank for sharing with all us geeks

//Mexico

[abolo1]

Bless your cotton socks.

[memadmax69]

Subscribed.

[TheBlackhawk2399]

well can we use two LM324's in series to amplify the output.What is the max Vcc

[TheBlackhawk2399]

For Wassup123: GND means ground or simply the negative terminal of your battery!SIMPLE

[LUVB6CPPgmodcsscoder]

quadraphonic

[Wassupbig123]

dont know *

[Wassupbig123]

sorry im a big beginner and i dont what is the GND and by the way sorry for my english im french

[mcguanlao13]

The video was awesome and I learned a lot. But I have a question (hopefully you'll answer back asap), how did you connect that earphones with the 3.5mm jack intact to the circuit. What specifically that "item" is called and how to connect that "item" to the circuit. Thank you very much. Keep sharing your knowledge. *Cat noises*

[kinsi55]

here´s some more cat noises :D

[mdesm2005]

why add "smoothing" capacitors if you use batteries? Batteries generate perfect DC (unlike rectified ac ). Is it the op-amp that can momentarily draw too much current from the batteries and that would make the voltage drop (w/o the caps)?

[Afrotechmods]

@mdesm2005 Yup. 9V batteries have significant internal resistance.

[MrSqwiggles1]

hi i don't really get the ground thing so good, i just get people telling me to connect ground to a piece of metal connected to everything or something like that. can you explain it to me so i understand, im just a novice at this stuff, im only thirteen.

[deagle94]

@MDSVes i know it goes to the ground, but in this circuit were does ground go to? to negative of the battery?

[Youcansuckme69]

Instead of using +/- 9V for the input power could you use 0/18V?

[rredbeak]

Can you make a video demo for microphone impedance matching after it leaves the audio amp?

Ty God Bless.. Rod

[rredbeak]

I love your series of videos,But can you please help me modify the output to 500 Ohms to feed my 500 Input CB please?

I know youre busy but a video on output impedances would be great TY God Bless Rod

[Pagweb]

How do you create a negative voltage with only one voltage source?

[TheSportsbot]

this guys funny. we're lucky he didnt choose standup comedy.

[rredbeak]

I want to learn HOW TO build a condenser mic through an audio amp THEN match the output to my 500 Ohm input for my CB radio.

Nearly all circuits output into a 8Ohm speaker.

Ive already learnt from your videos how to set the gain of the amp. But then im lost. I need [i imagine theres LOTS of other radio users too].

PLease help me with a impedance matching circuit with an output volume control.

God Bless.. Rod a CB radio nut

[BinaryLinux]

Need to build an amp to fix my subwoofer, so then I can listen to your irregular heartbeat.

[vochitoken]

Excellent tutorial, thanx!

[TheGuyInUrCloset]

Just wondering, why would you put a variable resistor after the entire circuit, instead of setup as R2? Wouldn't that set up a variable gain?

[Afrotechmods]

@TheGuyInUrCloset To give people who have never seen an op amp before the simplest possible example of a fixed gain circuit.

[TheGuyInUrCloset]

@Afrotechmods So then would it be more efficient to use a pot at the end or as R2? Are there any advantages to either of the two?

[Afrotechmods]

@TheGuyInUrCloset It would be the best to have a fixed gain of 10-20 or whatever and then have the pot at the input of the amp.

[TheGuyInUrCloset]

@Afrotechmods Thanks!

[666TECHNO666]

good circuit, the ones we built in electronics were twin output amplifiers, very simple to make, a few caps a couple resistors and the IC

[ingkiller]

5:05 nomnomnomnomnom

[davidenelson]

where would be the best place to place a potentiometer in this circuit to adjust the volume (input, output or gain). Because i would like to integrate this with a microcontroller to have a volume indictor on the side. So i would need a reference voltage. Please reply

[Afrotechmods]

@davidenelson Contrary to what is presented in this video, the better volume control circuit would be to have a fixed gain amp (e.g. gain of 10 to 20) and then use a potentiometer to divide down the input voltage.

[davidenelson]

@Afrotechmods I am actually making a transistor amplifer (class AB) which is even more confusing as so where to put it.

[deagle94]

@Afrotechmods hey brom got a newbie question , in 1:37, were you got the batteries, were does the ground go to, cause you got the + and -, and there is also a ground symbol. in a real circuit were would this "ground" go to?

[donttrytoclick]

Hi, i recently built that same amplifier according to your schematic. However, when i turned it on and touched the metal part of the microphone i heard radio noise of some talk show. Please reply on why this is happening.

thanks

[Afrotechmods]

@donttrytoclick Nice. You were picking up a nearby AM radio station. Your body can be a good antenna.

[Annakenskywalker]

fucking awesome man

[MrGunnaras]

very nice

[Gunner3210]

Your cat is a light sabre.

[b131188]

Thanks for this tutorial

[sprttch]

Can it be done with just one batt?Didnt understand the -9V. Cheers.

[jdflyback]

can you please tell me what is wrong with using one nine volt and calling the negative terminal ground?

[mamu7mich]

love the cat noises :D

[humxa24]

can i just power it with +9v and ground as it is non-inverting?

[R2Processor]

Hey so this works like a transistor or whatever the thing is called to move 120v to 9v or the other way around

[Knightmetal]

Here's a question that I'm sure has been asked before but I just can't find the answer here. Does the +9V used to power the mic have a different ground? are there two grounds in the circuit? don't be surprised by the question, I'm learning electronics, thanks.

[Afrotechmods]

@Knightmetal It should be the same ground i.e. they are connected somehow.

[reviathon360]

Hey Afroman,

I have built a 3band audio spectrum analyzer out of OPAMPS, and I am currently moving it to five bands using a bunch of 324's. I am using 324's as comparators and amplifiers, but I cannot use any other OPAMPS for some reason. I have one LM324 as an amplifier, and I need one more for my fifth band, but my TL082, and my uA741 do not work as non inverting amplifiers. the output just stays at high. Do you have any idea why?

[outwit2010]

I make this circuit with lm324 and gain of 100 and I hear lots of noise, But ne5532 with gain of 51 work very fine.

[dizzleblackizzle]

WHY CAN"T MY INSTRUCTORS EXPLAIN IT THAT WELL!!!

[slayerLM324555]

not to sound stupid but, where do i put the ground when using a breadbord

[patchcords]

I wonder if the LM386 only has one amp in it?

[ascott51088]

ha the cat tried to eat the microphone!!

[udiweizman]

Great stuff, love the cat bits :)))

[ocxic]

Awesome Vid, I have an issue though with the circuit, I'm actually using a 0372DP1 Dual op-amp, and running with +/- 12V power supply. and it works great the only issue is that when I power up the amp it blows up my head phones with a nice POP! what do I do to stop this, it's happened twice!! :(

[outwit2010]

@ocxic You must make a delay start circuit

[MrDankan83]

Afro you are the man.......!!!!

[alpha001ful]

Why do we usually want the resistor to be in Kilo Ohms ? I have set up the same circuit in my lab except i am trying to power small electric fans. Its not working . Any help ?

[Afrotechmods]

@alpha001ful  Lower resistances means more current needs to be drawn and that's easily avoidable. And a small signal op amp can't deliver enough current to power things like a fan.

[alpha001ful]

@Afrotechmods Thanks for the help. But i have one more problem.

I am trying to connect opamp to the fans motor. The signal is given from Labview program. I have followed exactly what is shown in the video. It is not working simply..What do you think the problem might be ? Any suggestion helps .

[Afrotechmods]

@alpha001ful An op amp is just totally the wrong thing for powering a fan - you want a proper motor speed controller, h bridge, pwm circuit, or something else.

[alpha001ful]

@Afrotechmods: Somebody suggested me that Mosfet is good. But it has non linearity. I am developing a PID controller in which an arm attached to the fan has to be rotated angainst a torsional spring. So the controller controls the voltage which consequently controls the angle travelled by the arm . fan takes volatge from 0-8.4 volts easily and current 0-6 amp. DAQ gives 0-12 volts but current in milliamps- current is the concern.i need a fairly linear amplifier (don't have to be too precise)?

[alpha001ful]

@Afrotechmods: Somebody suggested me that Mosfet is good. But it has non linearity. I am developing a PID controller in which an arm attached to the fan has to be rotated angainst a torsional spring. So the controller controls the voltage which consequently controls the angle travelled by the arm . fan takes volatge from 0-8.4 volts easily and current 0-6 amp. DAQ gives 0-12 volts but current in milliamps- current is the concern.i need a fairly linear amplifier (don't have to be too precise)?

[khoham]

@Afrotechmods well you're not looking at it like he may have.. maybe he should be referred to your video on the power comparator and peak detector circuits and the output can be put on the gate of a transistor to drive the transistor and he can just add a flyback protection circuit to the transistor.. this way he can control the on time using the peak detector circuit and use different ways to control the fan using the power comparator

[reviathon360]

@alpha001ful Connect the signal out to a resistor (20k-1k) to the base of a NPN transistor.

Hope that helped

[zombiepancakes21]

3:49 that cat made this video have a gain of 1000

[xato909]

cat gonna noom nom your mic :D

[RavenRof]

how is it amplifing if you giving it more volts than it is outputting? isnt that the oposite of amplify?

[Shalomyoyo]

You just explained to me what my lecturer has been explaining for the past 10 classes. Thanks.

[kijifled2]

Does anyone know if it is possible to use an op amp as the preamp stage in a power amplifier? Could you for example take the output of the op amp and connect it to the base of a bjt power transistor such as a 2sc5200/2sa1943 pair? Thanks.

[richardkalaf]

FINALLY i realized where i remember your voice from!! You´re the voice from K.I.T.T. , the car from "Knight Rider" .... :P

[GiorgioCapocasa]

"Negative voltage" really makes my head hurt.

I'm a total beginner, but how can voltage be negative in a battery?

Does it mean that it has less electrons than ground?

If so, how does the two batteries solution work?

Sorry for my silly questions :S

[grimmfactor]

@GiorgioCapocasa Voltage is a relative measurement. If you use two 9V batteries in series, and call the point between the two "ground" or your reference point, there will be 9V between one positive battery terminal and your reference, and -9V between your other positive battery terminal and your reference (aka ground). Ground is just a name and a reference point, it does not actually signify a quantity (or lack) of electrons.

[GiorgioCapocasa]

@grimmfactor This changes everything.

Suddently, it all makes sense (:

I set the reference 'ground' so the negative pole of the battery is 9v below it and the positive of the other battery is 9 above.

Awesome :D

Thank you A LOT for bearing me and my questions.

[humxa24]

mine works f9 but has alot of distortion.... can anybudy tell me how i can fix that?

[humxa24]

cani use 5 volts with your circuit? as the output is only 2 volts.....

[outwit2010]

can I use 10k pot to set the gain? So I can change the gain in real time.

[outwit2010]

there are lots of noise when I use tl071 with gain of 101.

[carlover961]

Silly cat, that's not food, that's a microphone!

[humxa24]

can u plz tell me some 8-pin op amps i can use with ur circuit, i have to use only one op amp thats why,__ the one u showed had 4 op amps in it and i dont need that many, thanx 4 great tutorial. subbed

[CassetteMaster]

@humxa24 I believe a 741 would work.

[Simcore999]

=)Thumbs-up, for the amplified kitty-bite

[Desmaad]

In the mic amp circuit, what's up with the bit that goes from the output into the inverting input?

[myno1fakeaccount]

This is verry funny and educational!

[RaulBillieJean]

very cool thanks for this !!!

[mahela1993]

Great video.. Thanks you! and I like your cat.

[XBENSTARX]

In Norway, an LM324 is about 40 cents (2 kroner) =)

[cd4600]

Best video on op-amps for beginners! I do have two questions, first, couldn't I use instead of a power amp to drive the speakers, a nice power transistor? What would be wrong with that? And second, is it best to adjust the output volume by using a potentiometer in the biasing configuration that sets the gain, i.e. raising and lowering the gain, or the way you used it, directly on the output? Thanks a lot!

[deafeningmrm]

funny dude :-) like the way you explain difficult things the easy way! but now i really would need another video with more mathematics 'n theory...

[tantou]

I seriously was yawning just before you had the cat yawning..

[ChicoDaRave]

I'm needing this exactly same circuit, but with low pass filter instead of high pass... someone can help me? Thanks

[leonardo1480]

the cat at the end looked like it was hungry, lol as for the video, it was very interesting and the tips was excellent to I had made a circuit like that during my college days and we used a 741 Chip at the time that was our favourite chip to use for this project

[fgdfhtrhg]

How can you get a minus volatage battery ?

[secretsather]

For a volume, could you just use a 100k pot at R2?

[joshstube]

I love your tutorials!

Could I use this principal (and this amp) to build a VOX-like input directed to a micro-controller's analog input?

(to turn on when a desired decibel level is reached)

If not, what roadblocks or additional equipment would I need?

Keep the tutorials coming!

It seems my decision on what to build next depends alot on finding great tutorials like yours!

[gaussman08]

LMAOOOOOO XD! this video is freakin funny

[StoesA]

3m50 hahahah :D

[outwit2010]

its work but can't drive my earphone. I use it as external mic for my camcerder

[ran6257260]

Cute Cat <3

Thanks for the tutorial, very helpful

[bcsupport]

could an op-amp circuit be used to increase a digital signal voltage level for longer transmission distances ?

[Afrotechmods]

@bcsupport Totally! But not the op amp I used. You would want a high speed buffering amplifier. Analog Devices, Linear Technology, National Semiconductor and Texas Instruments are good places to start looking.

[bcsupport]

@Afrotechmods Awesome. Thanks for your help, and your tutorials rock !

[Doghammer1000]

Lol 2:55, oven with Afroman's brain taped on it

[shopo34]

i found an interesting effect...ibuilt this minus the mic and micpower,replaced with a guitar jack ...when the jack was open and the volume set a certan position .i picked up very clear radio!!! just thought that was cool..

[thebteam300]

YOUR CAT IS SO CUTE!!!!!!!!!!

[beastlt12]

Well done. Thanks for the vid

[PhattyMo]

LOL @ cat NOM'ing the mic capsule. :D

[ShadowriverUB]

nom nom nom nom

[Knightmetal]

Hey guys I need help with this video, important to mention I'm not an expert in this field. The schematic diagram shows two +9V's, are they the same or do I need two totally different power supplies in the circuit? and also,if instead of a mic I connect an MP3 player, that means I wouldn't need the 5k resistor and that +9V power supply on the left of the circuit, right? the connection would be (from left to right) MP3-capacitor and the rest?

Awesome video by the way.

[barcoxx]

@Knightmetal You need two power sources, a negative, and a positive. Everything else you mentioned is correct.

[plavins1]

PLEASE REPLY!!! is lm324 the same as lm324n?

[slipperymagoo]

@plavins1 As far as I know, there is the lm324n and the lm324d. The N model has a slightly higher wattage and specs. It's listed in the datasheet.

[tehseenb10]

LM324 IC is a very help in my projects..

we can use single supply.

[reviathon360]

Could I just ground the -9v? 

[Serpico261]

@reviathon360 if you do this youre op amp cannot produce a negative voltage on the output, only positive

[Landotter1]

@Serpico261 All that happens is when you use a single supply, is the output becomes half of what it would be for a dual supply eg. a dual 9V supply will produce 9V + and 9V - for a total signal of 18V peak-peak..... a single 9V supply will produce a signal of 9V peak-peak, wich is half. with a sine wave, the only audible difference will be output level. It is better to use a dual supply but not necessary. If the chip takes 18 volts you can make that a single supply and not lose much signal.

[Serpico261]

@Landotter1 yes your right, i forgot to mention that the lm324 is a single supply op amp. If you really want acceptable audio, a push pull configuration in class a amplifier is a standard choice for simple audio amplifiers circuits. very easy and cheap to build, you dont even need an op amp, a FET, two transistors and minor misc....gives you actually good quality

[Landotter1]

I wouldn't use a gain of 100 ever. The chances of oscillation or a roaring sound are too great. If you use the op amp that he said to use, there are 4 seperate op amps in that package. I'd go with 20 gain from #1 20 gain from #2 and use the #3 as a buffer. Also use a board POT to vary the output to the power amp so you don't overdrive it. I'd do the same if driving ear buds with the op amp.

[Shoyrou]

What do you do with the ground? Where do you connect it?

[Landotter1]

@Shoyrou If you do a split power supply eg +9V and -9V Ground is for signal ground only. Tie all GND parts together and that becomes the (-) of your signal. If you use a single supply, +9V, the grounds go to the (-) on the battery. Notice the power amp he uses has a single supply. Tie the signal ground from your op amp to the ground of the power amp, and the (+) output of your op amp to the (+) input of the power amp. Good luck!

[Shoyrou]

@Landotter1 aaah ty

[Landotter1]

@Shoyrou You're welcome.... Hope it helped!

[Anathor666]

Question about 5k resistor from microphone to power supply - why 5k, not for instance, 1k?

[Afrotechmods]

@Anathor666 It could be anywhere from 100 ohms to 1 meg - I just found by experimentation that 5k gave me the biggest signal and resistances lower than that didn't give me any extra benefit.

[yoramstein]

The mic is built with tiny charcoal particals.It (cheap mics) is in fact a resistor that changes its resistance as voice causes presure on the particals.The change of resistance causes a change of resistance relation between the 5k resistor and the mic and therefor also change of the voltage at the mics output.(there are mics that work on princip of changing capacity (there are more cosly and their amplification should be done diffrently).

[hyperboogie]

I have a general question about the high pass filter (3:12) why is a resistor needed?

as far as I understand, the capacitor's impedance drops in high frequencies and increases in low frequencies thereby blocking/attenuating low frequencies, but why is the resistor needed? isn't the capacitor alone enough?

[Afrotechmods]

@hyperboogie Normally the resistor is needed to set the cutoff frequency but in this case it's also essential because it acts as a pulldown to ground, so the signal ends up swinging from -10mV to +10mV. If all you have is a capacitor sometimes the output floats around DC biases you aren't expecting.

[herctrap]

if your R2 100K was a variable resistor

and you havent use the 10K variable resistor

you will had also volume controll

but with power economy

am i right?

[Afrotechmods]

@herctrap yup

[voidmansions]

A perfect video. Informative, to the point, and also very droll. Full marks.

[V8Jagnut]

dam your cat is cute :D

[ForViewingOnly]

Simply the best tutorial/refresher videos on YouTube. Thanks Afrotechmodman.

[xxflinkxx]

Actually you can get op-amps that are rail to rail, so with +10/-10 your output can go all the way to +10/-10 too. You would have to look at the spec sheet to know for sure

[AlexMG54]

LOL at the brain thing. Was like wut? . . . then my brain dinged and I loled.

[karamba5702]

I love the cat addition to the video, thumbs up! :)

[TheBarathbushan]

i wish you were my teacher !!

[silverstream314]

I really enjoy your tutorials! Do you have any plans for making one about filters?

[daeva0123]

Thats made things so much more clearer! Big Thanks!

[Intosia]

Great stuff man! Great cat :D

[nlimchua]

2:16 to 2:26 => there is a error in your equation. Should be R2=Gain(R1)-1 (not '-1000' as your video shows...). Otherwise, you make great instructional videos, I'm a fan. - NC

[Afrotechmods]

@nlimchua The equation is correct because R1 is 1000 ohms.

[alitou001]

best tutorial ever ,please make more

[toffer1220]

you've got the best tutorial i've watched so far, very clear and entertaining. I never thought that was so easy compared when my professor used to teach us before..

[alabader741]

thanx !

[TommyDaB1G]

BEST TUTORIAL EVARRRR!

[Th33vilthing]

haha nice video, humorous stuff

[samanthms123]

how is ur output so clean ? i mean i get a lot of interference and noise.. did u use some kinda filter or something ?

[samanthms123]

what would happen if i replaced the the speaker with an LED ?? would it blink corresponding to sounds which are picked up by the mic ?

[ubuntututorials]

@samanthms123 It would, but you wouldn't be able to see much because the blinking would be too fast. You might be able to see the high and low parts of the sound.

[agentgates]

Hi, thanks for sharing this video. This is what I was looking for! I've got tired in the harsh theoretical lectures without basics. Finally something that I can use after first watch. :)

[samanthms123]

AT 1:38 , whats the difference between GND and -9V ? and whats the point of even having GND when you have -9V ?

Sam

[asdflax]

Do you have to use the power supply circuit you showed or can you just use a regular 9V supply?

[Abukodonozo]

Damn, I really enjoyed this, thanks!

[Rk17]

greAT video!! hahaha man that was funny! i was focused on the cat so much hehehehe

[wzbzbz]

This video is excellent.

[Senetus]

Hahaha the cat additions made the video really excellent :D otherwise very easy to understand for beginners too. I saw this in Hackaday

[snappex]

I just made this and most of what I was getting was the local radio-station... :)

Thanks for a great tutorial and keep making awesome videos!

[apc3161]

Great video, I love it when people explain useful concepts in an easy to follow method. Its make the theory later on bearable!

[drverieevil]

your video is useful and entertaining. Give a pat from me to pikachu! :)

[Afrotechmods]

He said mrrrrrrrp

[drverieevil]

yey PIKACHU!

[TheOddOne2]

Superb as usual!

[kenboy893]

catty! Ill buy him/her of u :)

[Afrotechmods]

Pikachu is priceless.

[MrPolinghir]

nice

[petipenner]

dude i love your cat :-)

[endesigner]

Cats and electronics rule! :D

[colinstu]

*angry breathing cat sound*

lol