LM3886 as a DC-amp ?

TroelsM · 21st March 2006, 08:51 AM

Hi.

I need a opamp that can be used with a single supply up to 50-60V and deliver up to 1A at DC.

I can't see any reason why the LM3886 couldn't be used, but as it is a "audio-amp" I might have overlooked something?

Any other suggestions? I need to be able to control the output to within 1mV DC over the entire 50V range... Is that possible?

Regards TroelsM

davidsrsb · 21st March 2006, 01:08 PM

The LM3886 is not unity gain stable, the minimum is ~20dB

There is no real difference between a power opamp and an audio amplifier. The dc input performance is not as good, but you can usually work round this.

TroelsM · 21st March 2006, 01:11 PM

Hi.

Thanks for your answer. Could you be more specific about the "DC input performance" ?

Any other ideas, other opamp better suited for this application?

Regards TroelsM

peranders · 21st March 2006, 01:16 PM

Can you tell us what you are up (then we may suggest something)?

TroelsM · 21st March 2006, 01:23 PM

It's pretty simple ( or is it...)

I need to control a voltage between 0 and 50V with an accuracy of 1mV... The input/control is either a digital signal og an analog signal.

I was thinking of using the LM3886 as an non-inverting amplifier amplifying from 0-5V til 0-50V (or 0-2V to 0-50V).

The output-current is under 100mA, but I would like an option for higher currents.

If there's no power-opamp that can do this I might have to make one myself. Any Ideas on how to do this? After all DC is not very "audio-like" and I'm not sure that an audio-amp would be the best option.

Regards TroelsM

pinkmouse · 21st March 2006, 01:29 PM

The OPA 541/8/9 will be more suitable, have a look at the datasheets, however getting that accuracy of output will not be so straightforward. Why do you need so much accuracy?

TroelsM · 21st March 2006, 01:42 PM

I'm designing a piece of test-equipment and I have en spec that states that the output us to be know within 1mV.

I know it's not a trivial matter, and in the end I might have to go with a lower precision.

I'll have a look at that OPA54X.

Regards TroelsM

TroelsM · 21st March 2006, 01:46 PM

The OPA541 seems to be perfect! Even comes with an apl. note that fits my purpose perfectly.

Thanks a lot!

Regards TroelsM

pinkmouse · 21st March 2006, 01:50 PM

Quote:

I'm designing a piece of test-equipment and I have en spec that states that the output us to be know within 1mV.

Ah, so the brief states that you need to know the output to within 1mV, i.e. an accurate meter on the output, it doesn't say you need to adjust it within 1mV.

TroelsM · 21st March 2006, 01:52 PM

Well, where are actually not sure on that :-)

There will be a 16-bit measuring of the actual voltage, but I would still like to be able to set it with an accuracy of 1mV..

But I see your point.

Regards TroelsM

21st March 2006, 08:51 AM	#1
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	LM3886 as a DC-amp ? Hi. I need a opamp that can be used with a single supply up to 50-60V and deliver up to 1A at DC. I can't see any reason why the LM3886 couldn't be used, but as it is a "audio-amp" I might have overlooked something? Any other suggestions? I need to be able to control the output to within 1mV DC over the entire 50V range... Is that possible? Regards TroelsM __________________ Need more time...

21st March 2006, 01:11 PM	#3
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	Hi. Thanks for your answer. Could you be more specific about the "DC input performance" ? Any other ideas, other opamp better suited for this application? Regards TroelsM __________________ Need more time...

21st March 2006, 01:16 PM	#4
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Can you tell us what you are up (then we may suggest something)? __________________ /Per-Anders (my first name) or P-A as my friends call me

21st March 2006, 01:23 PM	#5
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	It's pretty simple ( or is it...) I need to control a voltage between 0 and 50V with an accuracy of 1mV... The input/control is either a digital signal og an analog signal. I was thinking of using the LM3886 as an non-inverting amplifier amplifying from 0-5V til 0-50V (or 0-2V to 0-50V). The output-current is under 100mA, but I would like an option for higher currents. If there's no power-opamp that can do this I might have to make one myself. Any Ideas on how to do this? After all DC is not very "audio-like" and I'm not sure that an audio-amp would be the best option. Regards TroelsM __________________ Need more time...

21st March 2006, 01:29 PM	#6
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	The OPA 541/8/9 will be more suitable, have a look at the datasheets, however getting that accuracy of output will not be so straightforward. Why do you need so much accuracy? __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort


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21st March 2006, 01:08 PM	#2
davidsrsb diyAudio Member Join Date: Dec 2005 Location: Kuala Lumpur	The LM3886 is not unity gain stable, the minimum is ~20dB There is no real difference between a power opamp and an audio amplifier. The dc input performance is not as good, but you can usually work round this.

21st March 2006, 01:42 PM	#7
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	I'm designing a piece of test-equipment and I have en spec that states that the output us to be know within 1mV. I know it's not a trivial matter, and in the end I might have to go with a lower precision. I'll have a look at that OPA54X. Regards TroelsM __________________ Need more time...

21st March 2006, 01:46 PM	#8
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	The OPA541 seems to be perfect! Even comes with an apl. note that fits my purpose perfectly. Thanks a lot! Regards TroelsM __________________ Need more time...

21st March 2006, 01:52 PM	#10
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	Well, where are actually not sure on that :-) There will be a 16-bit measuring of the actual voltage, but I would still like to be able to set it with an accuracy of 1mV.. But I see your point. Regards TroelsM __________________ Need more time...

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