Crossover Biasing Compensating Diodes

[@andrewferg8737]

I'm still new to electronics as I only developed the interest about one year ago. Your clear and concise videos have been such a big help. Thanks!

[@AllAmericanFiveRadio]

Hi Andrew You might be interested in the Navy's Training Course, it is very good. Navy Electricity and Electronics Training Series www.richardmcwhorter.com/NavyTraining/

[@midmodaudio6576]

@@AllAmericanFiveRadio thank you for the link ! I'm a Navy veteran : )

[@jazzbassmc8043]

Hi, i love the way you explain electronics.

[@desmondantony1136]

Great, I was looking for the reason why the two diodes thank you very much

[@AllAmericanFiveRadio]

Glad the video helped. Thanks for your comment.

[@1oldtexan922]

Thanks so much. This explains a topic that has bugged me for years.

[@mrdouble]

Thank you very much. Great explanation

[@h0ll0wm9n]

Good topic, and nice job on presentation. In audiophile circuits, one sometimes sees another type of diode being used in those locations: LEDs. LEDs tend to be less noisy than the std. diodes.

[@AllAmericanFiveRadio]

+h0ll0wm9n Thanks

[@Dad-ij2qy]

Very interesting. Thank you for showing us what you discovered.

[@AllAmericanFiveRadio]

Thanks

[@kolinevans9127]

Very well explained thanks for sharing Now I’m left wondering if the resistor would work as well without the balanced power supply etc probably should try that. And another test I’d like to try is 4 diodes same configuration but move the NPN driver output to the center of the 4 so 2 above 2 below.

[@AllAmericanFiveRadio]

Thanks, and your welcome.

[@tectalabyss]

Thank you for another very well done and explained video Rick.

[@AllAmericanFiveRadio]

+Bobby Tectalabyss Thanks

[@eugenepohjola258]

Howdy. Very nice. Some may wonder why the 10 ohm emitter resistors. When the transistors warm up the B-E junction threshold voltage drops increasing the idle current. The voltage drop over the 10 ohms increases decreasing the bias current. The idle current will stabilize. To get more power the 10 ohms may be replaced with smaller values but not too small. The emitter resistor voltage drop increase must always be larger than the junction voltage voltage decrease running warm. Another way is to connect diodes in parallel with the 10 ohms. They will pass high power currents but not interfere with the thermal stabilization running idle. The trade-off is some introduction of distortion when the current commutes from the 10 ohms to the diodes. Another topic is that the upper transistor base can't climb up to full +12 V also limiting the available power. This problem may be overcome using a boostrapping circuit to elevate the base resistor potential. And again it is a trade-off. Bootstrapping means uneven loading of the push-pull also introducing some distortion. Regards.

[@AllAmericanFiveRadio]

Thank You.

[@AllAmericanFiveRadio]

And thanks for the information.

[@Learnelectronics738]

Great you video thank you

[@AllAmericanFiveRadio]

Thank you

[@chrischris6147]

thank you very much for all these vidéos

[@AllAmericanFiveRadio]

Thanks

[@roberttimms1193]

Thank you very much. I love your videos.

[@AllAmericanFiveRadio]

Thanks!

[@qzwxecrv0192837465]

thank you for another great video. now that I have learned new stuff the last month, I really want to get an oscilliscope for sure.

[@AllAmericanFiveRadio]

Thanks

[@kamleshchavan7451]

Great video, explained in a easy way, sir one thing I want to know, in place of oscilloscope, which application you have used to see the wave form

[@AllAmericanFiveRadio]

Thanks for your comment. This is the oscilloscope I used. Hantek 6022BE PC Based USB Digital Oscilloscope kzbin.info/www/bejne/pIKTXqV6aJ6srLc

[@kamleshchavan7451]

@@AllAmericanFiveRadio 👌ok

[@MsFireboy2]

Thanks for posting. With the two output transistors are these high current ones? BD137 and the BD138 come to mind?

[@AllAmericanFiveRadio]

Yes the BD137 and BD138 should work. Thank you, and your are welcome.

[@MsFireboy2]

@ Thank you.

[@Jerkwaad]

This was extremely helpful!! Thanks so much Rick. -Ragnar

[@skycarl]

That was interesting Rick, thanks. Also I noticed you are getting some use out of your new pc scope.......Carl

[@AllAmericanFiveRadio]

+skycarl Thanks Yes the PC oscilloscope has been working out quite well. It makes it real easy to capture pictures or videos. Trying to take a picture of an analog oscilloscope or a video of an analog oscilloscope is a real pain. I'll bet in a year or so they'll be a newer model PC scope with higher resolution, more features, and for about the same money.

[@seankennedy8506]

Why is the the base of first transistor tied to the emitter junction of the push pull stage? Is it something to do with feedback to keep the first stage biased properly?

[@AllAmericanFiveRadio]

The first transistor drives the two output transistors and the two emitter are bias and negative feedback

[@videomejoe]

Can you tell us about the feedback resistor design considerations used from output to input?

[@AllAmericanFiveRadio]

That is negative feedback designed to produce a more frequency flat response from that amplifier section. I have had amplifiers that had negative feedback at each section of the amplifier.

[@kbruin79]

Thank you for the explanation however it's not very clear how having the diodes will solve the problem.

[@AllAmericanFiveRadio]

It is interesting. Think about the 0.6 forward bias of each EB junction of the transistors and the two diodes. 0.6 X 4

[@FRRRRAAANNK]

Great video ! Thanks so much.

[@billybonewhacker]

as always very informative and interesting.

[@AllAmericanFiveRadio]

+billybonewhacker Thanks

[@natalerizzo9379]

The schottky diodes are indicated to correct crossover distortion?

[@AllAmericanFiveRadio]

Good

[@Thermionman]

this is very interesting! Thanks for the video

[@AllAmericanFiveRadio]

+Chris Shippam Thanks

[@hugoribeiro8281]

Very good explanation 😃

[@AllAmericanFiveRadio]

Thanks

[@ebuyuto]

What was the input signal consist of? I meant what was the input? A function generator or a PWM?

[@AllAmericanFiveRadio]

+De Sean Chambers Thanks The input is an audio generator at a Thousand Hertz

[@keithking1985]

thank you very much, that made good sense.

[@AllAmericanFiveRadio]

Glad you found the video useful. Thanks

[@Elios0000]

what about a resister and diode in parallel?

[@AllAmericanFiveRadio]

+Elios0000 Thanks You could use diodes and resistors in parallel, this would reduce the compensating effect of the diodes also temperature compensation. But that may be desirable depending on the purpose of your circuit.

[@christyanrachman8753]

finally I got an explanation about this

[@AllAmericanFiveRadio]

Your welcome!

[@Apple.Repair]

Thank you so much!

[@AllAmericanFiveRadio]

+Ali Hajinasiri Thanks

[@navinlessing7053]

thanks a lot for the video... could you leave a link for simulator so i can download and use it

[@AllAmericanFiveRadio]

Thank you, and your welcome.

[@RepairRadioLab]

thanks for explanation

[@AllAmericanFiveRadio]

Thank you.