Differential Amplifier, the Basics

[mirzaavdic]

Good video,great that you demonstrate it....:D

[AllAmericanFiveRadio]

Thanks mirzaavdic

[linuxford]

i like the simple schematics and the explanation, and using the scope is very cool .. thanks very much :)

[AllAmericanFiveRadio]

Thanks linuxford

[orbiter8]

Great explanation. Thank you.

[AllAmericanFiveRadio]

Thanks orbiter8

[vibra64]

You always present great videos on YouTube. I look foward to your videos.

Thanks

[AllAmericanFiveRadio]

Thanks vibra64

[skylon25]

Absolutely great video. Professionally done. I would love to see more of your videos.

[AllAmericanFiveRadio]

Thanks skylon25

[DigiSDR]

Thanks for bringing clarity to this subject. BTW, when the circuit it shorted, which component(s) of the circuit absorbs the audio energy. Just trying to figure out which component is taking all the stress (heat?). Joe

[AllAmericanFiveRadio]

Thanks DigiSDR

The load resistors are always in the circuit when the signals are the same or different. And so are the emitter resistors, but their for biasing the bases. The most signal will be across the load resistors.

[Albinorama]

Great as usual.

Please do some video about audio transformers, impedance transformes, etc.

THANKS.

[AllAmericanFiveRadio]

Thanks Albinorama

[shaofu424]

thanks man... seriously... peace...

[AllAmericanFiveRadio]

Thanks shaofu424

[palotitoe]

Excellent tutorial Rick! Clear and well explained as usual.

As long as you focus so well on basics principles, basement knowledge becomes strong enough to support more on top!

Thank you very much for your dedication preparing this learning material.

Best Regards. Pablo

[AllAmericanFiveRadio]

@palotitoe

Thanks Pablo,

The basics are super important. Everything depends on that knowledge.

Regards

Rick

[dmottern1952]

Rick - outstanding video.  Just finished the chapter on op amps with my students, where we talked about diff amps. Doug'

[AllAmericanFiveRadio]

@dmottern1952

Thanks Doug,

They are very interesting and useful too. Hope your class finds op and diff amps interesting. From the response I'm getting, a few YouTubers find them interesting also.

Rick

[ossopalatino]

Great tutorial!

[AllAmericanFiveRadio]

Thanks ossopalatino

[falcon02012]

Differential Amplifier is used in speaker phone to remove back ground noise.

[AllAmericanFiveRadio]

Thanks falcon02012

Yes, it seems like magic too.

[jenko701]

If you had two radio stations and if one of the stations bled over on to the other, in thery you could remove that station with a diff amp buy taking a clean copy of one of the stations signal and the copy that had both, run them through a diff amp and you could get rid of the unwanted audio and just get the audio you wanted. what do you think.

[AllAmericanFiveRadio]

Thanks jenko701

Sounds like it will work. Anything that is the same at both outputs is a null between the outputs. It should be greatly reduced or removed. This video is a simple example, there are chips that can do a much better job. I would Google the information.

[CassetteMaster]

I wonder if this could cancel out DC bias's background noise while playing back.

[AllAmericanFiveRadio]

Thanks CassetteMaster

That would be interesting to try, to remove white noise. It is in the background. That just might work.

[AllAmericanFiveRadio]

@CassetteMaster

Sounds like it will work. Anything that is the same at both outputs is a null between the outputs. It should be greatly reduced or removed. This video is a simple example, there are chips that can do a much better job. I would Google the information.

[joernone]

Very good job, Rick. Clear as glass. If I can understand it, anybody can.

Regards,

John

[Serpico261]

sir that was again great.I knew that differntial amps are constructed this way but i did not realize that this configuraion alone can perform this function. Is it really possible to just connect the two outputs together?

[AllAmericanFiveRadio]

@Serpico261

Yes. The output is not high. I ran the output from the transformer to an amplifier. At this point the output is low because it is the difference between the two transistor outputs. It is useful and it is easy to amplify. And the video is not fudged. what you see is what happened. The transistors are 2N2222.

[AndyDaviesByTheSea]

Hi Rick, nice clean demo. Have you ever stripped a sound off a recording like that? I can see the possibility but I could imagine that you’d get some heterodyning unless you could maintain perfect in phase sync.

Kind Regards ... Andy

[AllAmericanFiveRadio]

@AndyDaviesByTheSea

Hey Andy,

I don't remember if I have or not, it was an exercise and lesson in one of my Heath Kit courses. And yes with analog recordings this process is difficult. Today I would used digital recordings. Using my digital sound applications, I have sync-ed two sound sources, recorded by two different digital devices, of the same thing for over 10 minutes and they remained in perfect sync. I was amazed because I remember how difficult it was, now it is nothing.

Regards

Rick

[AndyDaviesByTheSea]

@AllAmericanFiveRadio Hi Rick, Yes, I guess if you can keep count of things it’s got to make it easier, never thought of that.

You say ‘... in one of my Heath Kit courses...’ I don’t know that they did course but I imagine that they must have been hugely informative; I’ll have to look into that a bit more it sounds very interesting. Ps did you see my ‘Soldering tip’ video?

Kind Regards ... Andy

[AllAmericanFiveRadio]

@AndyDaviesByTheSea

Hey Andy,

I don't know how many Heath Kit courses I have done, well over fourteen. About the last one was building an helium neon laser in the Laser course. About the last lesson in this course was using the laser to make a sound interferometer. I could hear myself walking and cars passing by the house. I made a video on the interferometer using a laser pointer. In another video using the laser pointer I audio modulated it and the sound quality is very good.

Regards,

Rick

[lawnmowerrecycler]

This is a nice, clear explanation of a circuit that I have always had a tendency to avoid because I didn't completely understand it. Now I do, thanks.

[AllAmericanFiveRadio]

Thanks lawnmowerrecycler

[bfestevao]

Thanks! 

[AllAmericanFiveRadio]

Thanks bfestevao

[barn5923]

This was very Educational I enjoyed it . Thanks////// I look forward to your videos. Thanks again.

[AllAmericanFiveRadio]

Thanks barn5923

[THEtechknight]

differential amplifiers are used in the majority of solid state push pull amplifiers. Why? dunno but they are.

[AllAmericanFiveRadio]

@THEtechknight

You can control the sound quality with the second input.

[hmerrett]

Could this also be used to remove anything that is center panned (e.g. vocals) from a stereo recording?

[AllAmericanFiveRadio]

@hmerrett

If you have just the sound you want to remove recorded, it is possible to remove it, one channel at a time. I think there are sound applications that can do this all in the computer today.

[k5cxo]

Super video as always Rick

[AllAmericanFiveRadio]

Thanks k5cxo