How to Bias an Op-Amp and Transistors: Bias Resistors
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- čas přidán 27. 02. 2021
- In this video, we will go over resistors used in a guitar pedal for setting the bias and what that all means.
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Holy crap, I've been trying to understand bias for YEARS because everyone just throws it around like we all know what it means but this made it click.
your aussie accent changed heaps!
Dude...I know I'm late to the party, but that was the BEST explanation of opamp biasing I've seen! I have a better understanding now. Strong work!
Brilliant explanation! I've seen quite a few biasing videos, and this one so far clarified exactly what is going on with Kirchhoff's and ohm's law in play, vs actually on paper. So I am grateful and appreciate you taking the time to make the video!
Glad you liked it. Just wanted to show some basics on building audio circuits
@@erikvincent5846 well you did that for sure, I've built a few circuits, but never quite fully understood the voltage offset, and the oscilloscope helped a ton. I guess I should actually buy one 😅
Man these videos are gold...hope to see more like biasing transistors, see wave forms, log pots, etc. thank you so much!
We did a video on transistor gain, which goes over biasing a bit. czcams.com/video/2m5wLM2sGoI/video.html
Best video I’ve watched from you yet, thank you
Great video, I actually understood everything. Gold standard tutorial.
Your videos are usually impartial but there was a lot of bias in this one.
Dad jokes... I might have to use that one.
man, I'm divided on how to react to this?
You explained it very well, thanks!
Great videos, this is awesome content
Excellent explanation
Thank you for this! Great to know the theory. I just finished my first circuit from scratch (to test my knowledge) and it’s a fuzz with a bias pot.
Glad it was helpful!
Great video!
So good! Thank you!
Thank you sir . I'm attempting to build a HiFi HP amplifier via tl072 buffer into a push pull 8050/8550 trany , and this helped along the way ,my concerns are of course impedance and clarity . I do know I may able to only achieve class B but I have seen this advertised as class A 😂😂
Good stuff dude!
Great video
It's worth mentioning that the Dan Armstrong's blue clipper uses an unbalanced voltage divider in order to get a distinctive sound.
Self bias Resistor by Fear Factory!
I was trying to find a way to force that in there. Unfortunately, that's an old vacuum tube theory implementation, and isn't even a thing in guitar pedals. That being said, Demanufacture is one of my all time favorite albums.
Amazing info. You helped me understand a great deal. Can you go a step further and show how one would set bias from an internal trimpot?
How about this video? czcams.com/video/yFq6GwrF9do/video.html
Thanks for the suggestion.
@@erikvincent5846 you, sir, are a gentleman and a scholar.
thanks
This is the first time I understand the Bias !! Great job. Is it the same process when we speak about the bias of valves on a valve amplifier ? Thanks again.
It is very similar
@@erikvincent5846 Thanks for your answer. Have a nice day.
Hi! Love the videos! I’m trying to build an npn bc108 fuzz face circuit and the when the switch is on and the light turns on the fuzz kind of works for like a second each time you strum but then cuts out and it also seems to miss notes entirely. Is this a result of the stock resistors not achieving the necessary bias value? Or is there something else wrong in my circuit? Any help would be greatly appreciated thanks!
on your second example you show moving the biasing voltage divider from the input, to the power supply . i was wondering since both resistors are now in the PSU why are we not able to simple use a jumper vs using that 2.2m going to 4.5 bias?
Hi! What does C5 (47u) do in the example where the Voltage Divider is moved into the power supply?
Would you have to do anything different with hard/soft clipping diodes for distortion when doing this biasing? And do you have to unbias it at the output?
Thank you for this video and clear explanation. I still hVe a hard time with the second bias example where the bias resistors are in the power circuit and there is a 2.2 meg in series before going to the op amp. My brain goes straight to dc theory. I you measure the voltage at the op amp is it still at 4.5V?
This is an old comment, but I'm having issues with this specifically. 9v supply, 10k resistors for Vr, then a 1meg "bias" resistor, and I'm getting 4.5 volts at Vr (good), 2.2 volts after the bias resistor/at the buffer input (bad/low?), but the buffer output is sitting at 4.5v (good)... not sure whats going on.
One thing I have always wondered. The C3 and R4 filter, you have that going to ground. Many schematics I see that filter going to the bias voltage. Is there a difference between the two methods?
Usually there isn't much of a difference. Usually it is a pcb trace routing decision.
3:30 how does one come to decide the value of the resistors that make up a voltage divider? What determines the rating?
As far as I understand you can use whatever value for a voltage divider, as long as both resistors have the same value it will then output half the voltage.
In the 2nd schematic, you have the bias resistor, R6, set at 2.2M. I have seen other pedals where that resistor can be as low as 100k. Does the value of this resistor matter much?
There are a few things to consider. One thing is if an RC filter is created. If so, how will it effect your EQ. Another is that high input impedance is often desired and bias resistors contribute to this. However, if too high, it might not pull up an op amp fast enough, if the bias voltage divider capacitor is too large.
Nice Video :)
I have a question, hopefully someone can help me here. Recently I finished a sunn model t preamp by fuzzdog. However all 3 of the internal trim pots were 47k even though the build doc said 2 if them should be 25k.
Does this make a difference in tone or/and functionality?
Thankfully, you are in luck. T1 and T2 on that circuit are just variable resistors, instead of voltage dividers, so you will just need to adjust them to 25k or below to set your bias on those JFETs.
do you have any videos were it's like a "let's build" of a small tube amp?
Check the channel name...
What application you use?
This is mostly using LTSpice.
what program is that
That's LTSpice. I have links in the description for the LTSpice playlist, which also include links to download it for free.
what the name of that software?
That is LTSpice. I will a link in the description with out LTSpice playlist, which can give you a primer on setting it up and using it.
@@erikvincent5846 nice,,thx..
@@kavtech_midi czcams.com/video/sN941dA_bWE/video.html
Tobias .... Tobias Onyango Fünke?
Arrested Dev?
That Fünke is some kind of something. Boy, this Fünke is all anybody's ever talking about. So sick and tired of hearing about how brilliant that Fünke is. ..