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Need help understanding a schematic

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Prithul0218:
I was looking at this schematic of a DC Load that Scullcom Hobby Electronics made. I couldn't figure out why they were using U7C. The OPA277 has fairly low output impedance, enough for an ADC, doesn't it?

I am asking it here cause Scullcom Hobby Electronics didnt reply.
Thanks.

Schematic source: http://www.scullcom.uk/design-build-an-electronic-dc-load-part-1/

anishkgt:
He may have explained it in his video.


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Prithul0218:
I went through all the videos. I don't remember that.

Zero999:

--- Quote from: Prithul0218 on February 04, 2019, 07:09:59 am ---I was looking at this schematic of a DC Load that Scullcom Hobby Electronics made. I couldn't figure out why they were using U7C. The OPA277 has fairly low output impedance, enough for an ADC, doesn't it?

I am asking it here cause Scullcom Hobby Electronics didnt reply.
Thanks.

Schematic source: http://www.scullcom.uk/design-build-an-electronic-dc-load-part-1/

--- End quote ---
It's just a way to use a spare op-amp in a quad package. It could be removed but then the spare op-amp would need to be configured as a unity gain buffer, with its input tied to 0V. If you're using separate op-amps, rather than the quad AD9630, then remove U7C and R11.

mvs:

--- Quote from: Prithul0218 on February 04, 2019, 07:09:59 am ---The OPA277 has fairly low output impedance, enough for an ADC, doesn't it?

--- End quote ---
More then enough to burn something downstream... I would put a resistor to limit current if the output goes negative (Vee is -5V). MCP3426 has diode clamps with 2mA abs. max rating, for AD8630 i have not found any data.

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