just thought of something:
is there any positive or negative effects of controlling the volume by changing gain "real time"?
repalcing the feedbackresistor with a pot if you get my drift..
just wondering realy..
is there any positive or negative effects of controlling the volume by changing gain "real time"?
repalcing the feedbackresistor with a pot if you get my drift..
just wondering realy..
The diodes can be something like 1N4007.
R1 and R2 depend on the choice of pas transistor.
Let me try to explain my understanding of how it works. Let’s start by assuming very little current is drown, say a few hundred milliamps. The voltage drop across R2 will be very low, thus the voltage difference between the base and emitter of the pas transistor will be to low to turn it on. As we increase the current drawn by the load the voltage drop across R2 increases and so does the voltage difference between base and emitter. When this difference exceeds the base emitter on voltage the transistor will start conducting. R1 limits the current to the pas transistor and prevents it from “stealing” to much current from the regulator when it switches on causing the drop across R2 to decrease turning the transistor of and so on. At least that’s what I think it’s there for, I’ve seen schematics both with it and without it.
R1 and R2 depend on the choice of pas transistor.
Let me try to explain my understanding of how it works. Let’s start by assuming very little current is drown, say a few hundred milliamps. The voltage drop across R2 will be very low, thus the voltage difference between the base and emitter of the pas transistor will be to low to turn it on. As we increase the current drawn by the load the voltage drop across R2 increases and so does the voltage difference between base and emitter. When this difference exceeds the base emitter on voltage the transistor will start conducting. R1 limits the current to the pas transistor and prevents it from “stealing” to much current from the regulator when it switches on causing the drop across R2 to decrease turning the transistor of and so on. At least that’s what I think it’s there for, I’ve seen schematics both with it and without it.
thanks!
I think i'v got it, the principle of it at least.
I will have to think a litle about how to figure out the eksact values of the resistors.
regards
marius
I think i'v got it, the principle of it at least.
I will have to think a litle about how to figure out the eksact values of the resistors.
regards
marius
Got some feedback from my teacher to day.
he explained the circut to me(not that it helped much..), and he got it the way that the current sharing transistor wont do much good as only a small current will flow through, and most of the current will still have to go through the regulator..
he explained the circut to me(not that it helped much..), and he got it the way that the current sharing transistor wont do much good as only a small current will flow through, and most of the current will still have to go through the regulator..
Not that I'm questioning your teachers opinion in any way, but this is a rather common way to increase the current handeling of lm317 or similar regulators. Just browse thru the datasheets at national and you will see dozens of similar configs.
yeah, well i do question him, but then again, he's supposed to know what he's talking about, though i find that teachers suprisingly often dont.
I dont quite see the logic he uses when explaining. he say's ohms law (whatever that is 😉, but i'm sceptic. he really isn't good at teaching stuff. everything i'v learnt this year exept for a litle microcontroller basics i'v learnt here and reading on datasheets.. schools..
I dont quite see the logic he uses when explaining. he say's ohms law (whatever that is 😉, but i'm sceptic. he really isn't good at teaching stuff. everything i'v learnt this year exept for a litle microcontroller basics i'v learnt here and reading on datasheets.. schools..
Hehe, questioning teachers and known facts is what makes most inovators, so keep that up 😉
In my book ohms law is what makes it work 😉 but he might be missing the fact that the regulator chip it self is current limiting at about 2 amps (lm317)
In my book ohms law is what makes it work 😉 but he might be missing the fact that the regulator chip it self is current limiting at about 2 amps (lm317)
Will do! 😀
argh!! I'ts so damn irretating not understanding this damn scematic!
I must have a complete understanding of something before i can work on it. it's why in school as well learning stuff.. well, no one said things would be easy.
argh!! I'ts so damn irretating not understanding this damn scematic!
I must have a complete understanding of something before i can work on it. it's why in school as well learning stuff.. well, no one said things would be easy.
DAMN! revelation!
i just had one of those lightbulb-hovering-above-head experiences!
i think i'v actually got it now.. though as for resistor values, i'l pull up my orcad, hope it has a voltage regulator, and if it does, get to work!
i just had one of those lightbulb-hovering-above-head experiences!
i think i'v actually got it now.. though as for resistor values, i'l pull up my orcad, hope it has a voltage regulator, and if it does, get to work!
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