Discrete audio amplifier project PT9 voltage amplification stage CCS

[@SmithKerona]

Hi John, the ringing is not from the supply independent CCS (two transistors CCS) or the function generator. Since the function generator has a relatively short rise time, your ground lead on your scope's probe will introduce artifacts. This is because the probe's ground lead has significant inductance which can't be neglected at the frequencies such rapid rise time produces. All the ringing you noticed is that classic signal integrity issues introduced by improper probing. Shorten your probes ground leads and try it again. Note also that, both of your circuits have high input impedance verses the function generators low impedance (50 ohms) which will introduce transmission line effects. I hope this helps and keep up the good work!

[@MrAlFuture]

Hi John. I'm really enjoying this discrete amp project. The way you're breaking down the building blocks and comparing alternative implementations is really enlightening. Thanks!

[@laredss]

Not sure if you mention it somewhere in the video. But the CCS with 2 transistors can be further improved. Turn one of the transistors around so they have the flat sides against each other. Then put a heatshrink tubing around them to make them thermally equal. Then you would have even less play in the constant current.

[@marijntopgear]

I love it when John tells me to grab the right knob!

[@100amps]

Heya John. Yeah, I’m riding the fence on these but slightly favouring the 2 transistor ccs. The ringing is pretty low and might improve on a pcb. Choice of transistors might make a small difference too. I’ll have to think more about this. (Not an engineer, self-taught hobbyist.)

[@jimhough6233]

Maybe Snickers senses a gremlin in the room with the meter.....He didn't want to stand & fight. I would love to see a MOSFET amp too! Cheers!

[@withoutl7980]

just a curiosity question, I am learning quite a bit about amplifiers through your videos and want to thank you for it. But the question I want to ask is, could you instead of a biasing transistor use 4 diodes and get a constant 2.8 V drop on them and by doing so bias the output transistors? Thanks :)

[@NoName-yy1jx]

Why there is no biasing circuit for the CE circuit? Another question if the differential stage doing all the voltage amplification with the help of the feeding back circuit why using CE circuit why not emitter follower circuit thank you for this amazing series

[@jbarker2160]

Could you improve dropout by using PMOS devices in the CCS?

[@johnyang799]

Would you talk a bit about global feedback of opamp + discrete and stability? That will be helpful.

[@JohnAudioTech]

Yes. When I get the full amp assembled, that is when global negative feedback and stability can be covered.

[@johnyang799]

@@JohnAudioTech That's nice!

[@TheTrueVoiceOfReason]

Hey John! First off, I hope you had a good Thanksgiving. Second, I know you went over it in a previous video of this series, but would you explain again the split resistor / capacitor alternative to a CCS? And when would this even be considered given the simplicity of either of the 2 CCS circuits you've shown today? Love seeing Snickers. "Feeltech." Lol "Got to grab the knob." Glad I wasn't in mid drink when you said that. :D Great out-take there. Hehe

[@TheTrueVoiceOfReason]

BTW, this is where you explained the Bootstrap alternative, in case anyone wants to know. kzbin.info/www/bejne/f2OpgmCee9V7b8k Still, though, what are the pros and cons of the passive Bootstrap vs. the active CCS? And why would you use one over the other in a given situation? (Trying to stimulate conversation - :) )

[@paulpaulzadeh6172]

Hi John , you can do also with depletion mode mosfet , Walt jung in his pepper show cascode version I use it, microchip have that mosfet

[@codydowling1120]

Hey John, it may be that the reason you’re seeing the ringing on the oscilloscope is because you’re attempting to measure a square wave with a standard probe with a long alligator clip. Additionally the circuit is mounted on a breadboard which has significant parasitics. If you were to measure with a differential probe or even install a pigtail/ground spring (shown here electronics.stackexchange.com/questions/136123/how-do-you-attach-an-oscilloscope-ground-spring) in place of the alligator lead on your scope probe it would likely cleanup noticeably for you when you measure it on the front of the function generator. However, when you measure it in circuit, the other parasitics - particularly inductances in the bread Board and lead wires will still likely give you trouble. That should clean up nicely in a good PCB.

[@boonedockjourneyman7979]

Square waves and breadboards don’t mix. You can actually measure both the capacitance and the capacitance distribution from hole to hole and run to run. Given how simple these circuits are, there’s no excuse for not protoboarding both and using proper probing methods. That ringing could easily show up on either circuit using your methods.

[@JasonLeaman]

Time to Upgrade that Signal Gen. I'm ordering the Siglent SDG810 for Christmas, I have the same one you do and it's not good for working on audio. Way to noisy.

[@KissAnalog]

Siglent is a nice unit

[@JohnAudioTech]

I looked at the nicer sig/arb gens from the other scope companies. If you look closely at the specs you see the distortion is too high for audio work. They are quality devices but are geared toward RF. You can generate clean sine waves in the audio band with a computer's sound output and square waves with a micro controller or logic gates.

[@aksela6912]

@@JohnAudioTech How low distortion/noise is low enough? Will quantization noise from a 12 or 16bit DAC be problematic?

[@johnyang799]

@@aksela6912 maybe not with 16bit but in most design 12bit can bit a problem. As their design goal is not for audio. Like affordable 100 dollar dongle can provide near to 0.0001% thd+n figure (real life tested)at 1khz and you will probably not going to find one even over 100 thousands dollar equipments.

[@aksela6912]

@@johnyang799 Hmm. I was thinking about using an Arduino, but they're limited to 12bit. 16bit would require a separate DAC and more involved code, increasing complexity a bit. Still might be a worthwhile avenue.

[@Elnufo]

Feeltech! Feel the Snickers! :-D

[@johnsenchakinternetsecurit8935]

"You got to grab the right knob" That's what she said !

[@aksela6912]

Surely "that's what he said"?

[@lex_parsimoniae]

Man I love Snickers.

[@DAVIDGREGORYKERR]

What about a Class A amplifier using 2xMJ3055 power transistors and a BD132 PNP google for 5 Watt Class A amp and see what you think.

[@GnuReligion]

Have seen the const-current symbol on the high side of B-output stages all over the place, but have not seen how it is simply implemented until now. Thanks ... but still, am left confused. Where does the Base resistor end up? Are you going to produce a -2V drop from the top, or tie it to the ground? I suppose what you demonstrate, is like this image (right), with 0.7V/68ohm yielding ~ 10mA: www.talkingelectronics.com/projects/TheTransistorAmplifier/images/Fig71ba.gif But your voltage is both above and below the illustrated 6-15v range. Well, you have done the rubber diode, and now this CCS. All that is left is a re-cap of a class-A, collector amp on the low side. Hmmm, how to get a gain of over 15 without noise? Complimentary pair?

[@kkathulgangadharan2262]

Sir please help me like to build a home theatre.for that me need a 6 channel audio amplifier. Please help me to select a good ic for my purpose.

[@JonathanGerardDias]

Tda2030 bridged since youre from india more readily available in my experience.

[@kkathulgangadharan2262]

@@JonathanGerardDias then what ic for subwoofer?

[@kkathulgangadharan2262]

Can i get a contact number of you sir?