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Products => Test Equipment => Topic started by: Jester on November 11, 2016, 08:59:24 am

Title: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: Jester on November 11, 2016, 08:59:24 am
I half expected to find a small ready made board on ebay using a LM3886 or similar but no luck so far.

I will be using this at 60Hz

Any suggestions?
Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: Vgkid on November 11, 2016, 09:08:01 am
Are you up to building one?
Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: Jester on November 11, 2016, 09:20:08 am
Quote from: Vgkid on November 11, 2016, 09:08:01 am
Are you up to building one?

I built a higher current version in the past (4 amps) based on the LM3886, that was a while back and I can't seem to find it or any blank boards. I hoped to find an OTS board or instrument.
Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: 2N3055 on November 11, 2016, 09:53:30 am
Quote from: Jester on November 11, 2016, 09:20:08 am
Quote from: Vgkid on November 11, 2016, 09:08:01 am
Are you up to building one?

I built a higher current version in the past (4 amps) based on the LM3886, that was a while back and I can't seem to find it or any blank boards. I hoped to find an OTS board or instrument.

Care to share a bit about design? Sounds interesting...  :popcorn:
Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: Vgkid on November 11, 2016, 09:54:19 am
Are you looking for any stsbility or accuracy requirement?
What about a precision diff amp with a high power opamp buffer.
Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: 2N3055 on November 11, 2016, 09:59:36 am
Quote from: Vgkid on November 11, 2016, 09:54:19 am
Are you looking for any stsbility or accuracy requirement?
What about a precision diff amp with a high power opamp buffer.

LM3886 IS basicaly a power opamp with minimum 10x gain.... DC specs are fully specced, and if you servo it with a low offset opamp it does a pretty good job... 

I'm contemplating about 4 quadrant power supply based on LM3886 for some time now... Didn't have time so far to do it yet ...
Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: Jester on November 11, 2016, 01:07:52 pm
Quote from: 2N3055 on November 11, 2016, 09:53:30 am


I built a higher current version in the past (4 amps) based on the LM3886, that was a while back and I can't seem to find it or any blank boards. I hoped to find an OTS board or instrument.


Care to share a bit about design? Sounds interesting...  :popcorn:

I designed it some time back, I don't recall the details of the CT.


Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: Jester on November 11, 2016, 01:33:02 pm
Quote from: Vgkid on November 11, 2016, 09:54:19 am
Are you looking for any stsbility or accuracy requirement?
What about a precision diff amp with a high power opamp buffer.

This will be used to calibrate an ac current measurement circuit, so short term stability (as in a few seconds) is all that is required. Accuracy is not super important because the actual current will be measured with an accurate meter.
Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: Jester on November 11, 2016, 04:17:22 pm
I will order a board based on the original design, if anyone needs a board let me know and I will order an extra
Title: Re: AC Current source (regulated) 200ma (load = 12-100 \$\Omega\$ resistive)
Post by: Jester on December 04, 2016, 01:20:29 am
Boards are in, crude but effective. I populated the board with 25V electrolytic caps, which limits output current to about 3A rms, I will need to upgrade the capacitors to 50V if I need more current in the future.