And just to add one more note regarding the explanation of circuit operation. An op-amp is an analog device that smoothly changes its output voltage; therefore it is not appropriate to say "logic high output" which "turns on the transistor". The op-amp senses the change in its input differential voltage and instantly reacts to it by starting to change its output voltage until it restores the equilibrium.
Well presented. Only critique would be the dismissal of the transistor emitter current not being the same as the collector. Depending on the load, the base current isn't going to be seen by the load. Basically, the R2 current will not match your LED current. The R2 will have the base current going through the R1 resistor from the opamp. If you want to perfectly calculate, you would move the LED to the emitter of Q1. With a high gain transistor, this difference will be negligible, but when running power transistors with gains around 100 you might want to compensate for the extra current.
A great movie! Just to note that when there is a permanently connected load there is no need for a base resistor because the transistor itself limits the base current by increasing the emitter voltage.
what if the VS for the op amp VCC has lower than VCE on the BJT? do I need some circuit configuration. example like VS = 12V, and the VCE is around 80V or above
Dang it lol, I'm trying to drive an LED circuit that requires a constant current at around 2A using 48V as Vref. The calculated power dissipation for the discrete components is obviously off the charts. Is there any other constant current regulator circuit that can be used for higher current applications?
Not really .... Once the load current reaches the set value , this will produce voltage across it equals the ref voltage = zener voltage this will switch of the transistor before the voltage across the load reaches Vcc so the load will never experience 14v across it
@@ThomasHaberkorn ok ... lets take it point by point you use the Zener to set the voltage you want across R2 this is your starting point if you want 5v across R2 , you buy 5.1v Zener or if you want 9v across R2 , you buy 9.1v Zener at zero second , there is no voltage of current across R2 once the supply starts , the transistor is ON and the voltage across R2 starts to build up to reach VCC but .... before that happens , once R2 Voltage reaches Vzener , the transistor will switch off so the current will drop once it drops , the transistor will switch on again and so on Why R3 ? it is to limit the Zener Reverse Current within an acceptable value ... otherwise it will burn , just like you do with an LED you put R3 in order to keep the Zener reverse current between 1 and 10ma , usually 5ma so if your supply voltage is 12v , R3 = 12(v) / 0.005(A) = 2400 Ohms (2.4k)
Hello, i followed all of your videos about current limiting circuits but all have the disadvantage of not being able to control high current. For 10Amps , which one do you recommand ? Thanks !
hi bhai, i have 24 votlage solenoid, if check the voltage near solenoide it is showing 24v, and if i check current it is varying from 0 - 650 mV, the coil is mounted on the hydraulic jack which is controlling the speed of jack, and the coil is being controlled by potentiometer, how can i make the circuit to make it happen,
@@rizvanrazi4698 Of course. But my point is a solenoid is a device controlled by current. (Not voltage) Sure, they print a voltage on it because the manufacturer knows the resistance of the coil (for DC) and most electric sources are voltage sources. If your source is AC it's already different. Did you find a circuit online yet?
And just to add one more note regarding the explanation of circuit operation. An op-amp is an analog device that smoothly changes its output voltage; therefore it is not appropriate to say "logic high output" which "turns on the transistor". The op-amp senses the change in its input differential voltage and instantly reacts to it by starting to change its output voltage until it restores the equilibrium.
Well presented. Only critique would be the dismissal of the transistor emitter current not being the same as the collector. Depending on the load, the base current isn't going to be seen by the load. Basically, the R2 current will not match your LED current. The R2 will have the base current going through the R1 resistor from the opamp. If you want to perfectly calculate, you would move the LED to the emitter of Q1. With a high gain transistor, this difference will be negligible, but when running power transistors with gains around 100 you might want to compensate for the extra current.
This was pretty cool! Care to do a practical application of this circuit? R2 would be a 20S/82v li-ion pack. Max charge current would be 60 amps.
A great movie! Just to note that when there is a permanently connected load there is no need for a base resistor because the transistor itself limits the base current by increasing the emitter voltage.
Awesome video, keep up the good work ❤️
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what if the VS for the op amp VCC has lower than VCE on the BJT? do I need some circuit configuration. example like VS = 12V, and the VCE is around 80V or above
Great video. Thanks
Thank you so much for watching!! Please don't forget to subscribe to our channel
Thank you for this beautiful video. Any help for high current applications?
No, this for low current only
Nicely explained
Can you suggest some improvements in the circuit ?
Finally I able to understand
Very informative video.
Pls. use color font without background shading for subtitles which make enable to see portion of diagram behind it.
So how to design a protected 4-20mA current source
Can u plsssssss make a video explaining on how to vary voltage n vary current in this system
Can we use this kind of system for a welding machine design of 0-200A and 0-50v ?? How can we varu thecurrent and voltage
Dang it lol, I'm trying to drive an LED circuit that requires a constant current at around 2A using 48V as Vref. The calculated power dissipation for the discrete components is obviously off the charts. Is there any other constant current regulator circuit that can be used for higher current applications?
use PWM LED drivers
@@FoolishEngineer Thanks!
6:28 is Vref in the load current equation the average voltage seen by the load? Because it in theory should toggle between 0 and 14 Volts, right?
Not really ....
Once the load current reaches the set value , this will produce voltage across it equals the ref voltage = zener voltage
this will switch of the transistor before the voltage across the load reaches Vcc
so the load will never experience 14v across it
@@alaanoor3679 good point. But I can't yet see weight Zener voltage is voltage of R2... I mean there's also load resistance and R3 involved here
@@ThomasHaberkorn
ok ... lets take it point by point
you use the Zener to set the voltage you want across R2
this is your starting point
if you want 5v across R2 , you buy 5.1v Zener
or if you want 9v across R2 , you buy 9.1v Zener
at zero second , there is no voltage of current across R2
once the supply starts , the transistor is ON and the voltage across R2 starts to build up to reach VCC
but .... before that happens , once R2 Voltage reaches Vzener , the transistor will switch off
so the current will drop
once it drops , the transistor will switch on again
and so on
Why R3 ?
it is to limit the Zener Reverse Current within an acceptable value ... otherwise it will burn , just like you do with an LED
you put R3 in order to keep the Zener reverse current between 1 and 10ma , usually 5ma
so if your supply voltage is 12v , R3 = 12(v) / 0.005(A) = 2400 Ohms (2.4k)
@@alaanoor3679 awesome explanation, thanks 😊
@@ThomasHaberkorn Glad i can help Thomas
Is there some reason not to use a lower voltage zener? Wouldn't that reduce the power dissipated in R2?
And how much is the total voltage drop of this circuit? Can i use a 3,7 volt battery for this circuit?
Nice Video!
Thanks!
How do you make sure the transistor is in linear region please
By adequate (normal) current through the emitter resistor.
How do you build a high current regular?
Thanks men
Can you use a mosfet instead of a bjt?
yes
Hello, i followed all of your videos about current limiting circuits but all have the disadvantage of not being able to control high current. For 10Amps , which one do you recommand ? Thanks !
I have also same question
Can you please clarify
What software do you use for the animations?
Hi, is this a switching or a linear circuit?
bravo....
What is the software you used for simulation?. Thanks in advance.
LTspice
hi bhai, i have 24 votlage solenoid, if check the voltage near solenoide it is showing 24v, and if i check current it is varying from 0 - 650 mV, the coil is mounted on the hydraulic jack which is controlling the speed of jack, and the coil is being controlled by potentiometer, how can i make the circuit to make it happen,
First you will have to consider that 0-650 mV isn't a current.
Then, Google is your best friend. There tons of resources for driving solenoids.
@Oscar Gr bhai it was a typing mistake it 0 - 650 mA
@@rizvanrazi4698 Of course. But my point is a solenoid is a device controlled by current. (Not voltage)
Sure, they print a voltage on it because the manufacturer knows the resistance of the coil (for DC) and most electric sources are voltage sources.
If your source is AC it's already different.
Did you find a circuit online yet?
Hi, wish topology is better for 3A charger?
PWM
Ac constant current source circuit plz,
Thats what the video is about FFS.
whats the max AMP this circuit can control?
Depends on the Power handling capability of transistor
Why did you choose 6.2v zener instead of 2.2v zener since the zener voltage should be the same with the load voltage
😘😘😘
Bhai!!