Author Topic: High power opamp current sinking (OPA549)  (Read 6154 times)

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Offline SpikeeTopic starter

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High power opamp current sinking (OPA549)
« on: September 30, 2014, 05:29:37 pm »
Hello,

I was looking (again) to build a dc supply using the BB (TI) OPA549 chip. In an old topic of mine someone said that i could also sink current.
So for example we want to use it as a dc load now , how would that be done ?
Connect DUT to the OPA549 -> turn input voltage of opa549 to 0v ? and just set a current limit ? or how do such things work?

Circuit:


Datasheet:
http://www.ti.com/lit/ds/symlink/opa549.pdf
Freelance electronics design service, Small batch assembly, Firmware / WEB / APP development. In Shenzhen China
 

Offline Kevin.D

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Re: High power opamp current sinking (OPA549)
« Reply #1 on: September 30, 2014, 08:07:06 pm »
 Just seen the cost of those things :o.Youl cost yourself a fortune using those ,It's power dissipation capability is not that good  if you look at thermal details .
 Stick to discreet transistors . If you want both source and sink capability then make a discreet mosfet push pull output stage  ,study output stage of opamps for an idea.
 

Offline SpikeeTopic starter

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Re: High power opamp current sinking (OPA549)
« Reply #2 on: September 30, 2014, 10:51:59 pm »
5/10 usd for 75W of current sinking is not that bad. If you do the current limiting using an external opamp and mosfet 100W should be possible.
Freelance electronics design service, Small batch assembly, Firmware / WEB / APP development. In Shenzhen China
 

Offline SpikeeTopic starter

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Re: High power opamp current sinking (OPA549)
« Reply #3 on: October 01, 2014, 09:29:45 am »
There is a lot of old stuck in russia/china. See ebay aliexpress. Thank you for suggesting mosfet push pull (never heard of it) it seems it can get pretty linear output with some tricks. The hard part is to get good output at low voltages.
Freelance electronics design service, Small batch assembly, Firmware / WEB / APP development. In Shenzhen China
 

Offline ondreji

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Re: High power opamp current sinking (OPA549)
« Reply #4 on: October 01, 2014, 10:57:49 am »
I was looking at it (OPA549) but I didn't like it for some reason... Maybe current limiting or something like that. Then I found nice LT1970 based 4 quadrant PSU application note: ftp://ztchs.p.lodz.pl/PRP/PRP_2006_2007/10804di.pdf

I would like to build it soon - about to order the parts
 

Offline SpikeeTopic starter

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Re: High power opamp current sinking (OPA549)
« Reply #5 on: October 01, 2014, 12:21:12 pm »
Nice find, thanks for sharing!
Freelance electronics design service, Small batch assembly, Firmware / WEB / APP development. In Shenzhen China
 


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