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I'm trying to find out what this part could be. It has the marking CMAR on top and nothing else other than an orientation mark. There are three of them in a filter I'm trying to identify. Because I don't know what the part is I'm not 100% sure what the filter is but it's one CMAR, an inductor parallel with a tiny capacitor, another CMAR, another inductor/capacitor pair, and another CMAR all in series. It comes right after a frequency mixer. enter image description here

The top right pin is the input, the bottom left is output. They are connected with a parallel resistor/capacitor pair. Bottom center goes to ground. Top left gets voltage (usually about 2.7V) and bottom right always gets half of whatever top left is. Top center is an enable pin. The setup around the part is perfect for it to be an op-amp with enable but I cannot find any sheets for a part with CMAR as the top mark. If it is an op-amp, it would be set up for AC coupling with a bias voltage coming to the bottom right. Any help with finding this is appreciated.

Addition:

I'm putting in a drawing of the whole filter that has CMAR in it to help get an idea how its used. I don't know what frequency range it's operating over sadly.

enter image description here

The main input comes from a frequency mixer just before it as I mentioned, and its output is sent into a logarithmic amplifier. The pins labelled V1 are all connected as well as the pins labelled EN. V1 is the main supply voltage and is usually 2.7V while EN appears to be an enable input. V2 is usually 1.35V (or whatever half of V1 is). I hope this info helps.

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  • \$\begingroup\$ Hmm, marking "CM" in SOT23-6 would be a Ricoh RP152N012A 2.8V/2.6V dual linear voltage regulator. \$\endgroup\$
    – rdtsc
    Jul 9, 2021 at 17:57
  • \$\begingroup\$ @rdtsc The ground on that part sadly doesn't line up with this one in the circuit. Thank you though! \$\endgroup\$
    – Jungush
    Jul 9, 2021 at 19:56
  • \$\begingroup\$ What frequency range is the signal on? What is the device? Can you trace the circuit and post it here, or least show us more of the board so someone can trace it? \$\endgroup\$ Jul 9, 2021 at 22:47
  • \$\begingroup\$ @BruceAbbott I added a drawing of the part of the circuit this part is in, I hope that helps. \$\endgroup\$
    – Jungush
    Jul 12, 2021 at 14:03

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The package looks like those made by Microchip. The marking code for MCP6293 is CMNN, where NN is the 'Alphanumeric traceability code' which could be any combination of letter and numbers.

enter image description here

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  • \$\begingroup\$ Looks like that's it! Thank you. What made it look like packaging from Microchip? \$\endgroup\$
    – Jungush
    Jul 13, 2021 at 12:07
  • \$\begingroup\$ The rounded corners, rough surface, dark laser etching, and 'necked' pins were typical of Microchip parts found in my google image search. Here's the hit that got me pointed in the right direction:- eevblog.com/forum/beginners/what-is-a-ajk0(or-o)-sot23-6 \$\endgroup\$ Jul 13, 2021 at 21:18

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