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Topic: buffer amplifier aka voltage follower with transistor or mosfet (Read 1 time) previous topic - next topic

zmay2509

Hello, Im working on a arduino controled power supply 0-30v
Im using pin 9 of arduino to analog write value (0-255) 0-5v conected to base of npn transistor then I use low pass filter to get analog voltage and this part works great but I cant draw much current because R2 and low pass filter.
I want that power supply can deliver 3amps or so.
On internet I found  buffer amplifier that uses op-amps and that is okey for 100-200mA, insted op-amps I want to use transistor or mosfet.
If you have some idea what to do or some experience please let me know.
Sorry for english, Thank you.


MorganS

How much current do you actually need? What bandwidth (how quickly does the desired output change?)
"The problem is in the code you didn't post."

MarkT

Normally for higher current you simply add an emitter-follower in the output circuit of the opamp,
so that feedback is taken from the output of the emitter follower.  A small capacitor may be required
to provide high-frequency feedback before the emitter-follower to make up for the sluggish
bandwidth performance of big transistors.

A source-follower can also be used.

For high power analog supply like this you have to worry about heat dissipation - you definitely
want analog, not switch-mode supply?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

zmay2509

i would to be capable draw 2-3 amps, time between change 1-2 sec.
I want to control voltage with arduino (0-30v 3A) so switch-mode supply I gues can be used to but I dont have knowledge to make one have you schematic?

MarkT

Whether switch mode is appropriate or not depends on whether the load tolerates the kind of noise
a SMPS generates - audio amps will not, motors don't care, heaters don't care, LEDs don't care... 

Perhaps you should explain what your load is going to be?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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