SMD part marked as R8W. What is it ?

[kripacharya]

I hate to cross-post, but really need this info now and tearing my hair out with no concrete result.

This is an SOT-23 (or similar) package, and used in an RF circuit of 100Mhz range.



Is it possible I am mis-reading the markings ?

 

[jiripolivka]

Looks like a transistor. Can you follow the PCB to find appropriate bias resistors?

 

[FvM]

None of the well-known types listed in SMD code book. Usual procedure:
- indentify circuit function
- find out polarity and most likely component type (BJT, JFET, MOSFET, diode(s), other

 

[kripacharya]

Looks like a transistor. Can you follow the PCB to find appropriate bias resistors?

None of the well-known types listed in SMD code book. Usual procedure:
- indentify circuit function
- find out polarity and most likely component type (BJT, JFET, MOSFET, diode(s), other

trust me when I say I have done all of the above. Thats why it's so annoying, and why I posted twice.

Best possibility I could find was BFG93A, but thats in a SOT-143 package, unless there's an SOT-23 option someplace ?

I don't think it's diodes, since there's several SMD's marked A7s which are BAV99's (dual ultra-fast diodes), so why would the designer choose a different one here.

Also there's a 6T, which is an MMBFJ310 Jfet, so why choose a different fet here.

That leaves PIN diodes or BJT's. But I can't find any which match the markings !!

Circuit decoding without knowledge of pinout is difficult at best, but I'll give it another shot.

Any chance it is some sort of 3-pin IC with a more complex functionality ?

 

[FvM]

You'll find various analog ICs in SOT23 package, e.g. voltage references or reset generators, so that's definitely an option.

Marking is manufacturer specific (except for some popular parts where many manufacturers are using the same marking, e.g. said A7s = BAV99).

Identifying circuit function is an interactive process, so I fear we can't support it effectively from a distance.

Knowing the instruments purpose, origin and age can possibly narrow down the manufacturer and type choice a lot.

 

[kripacharya]

Ok, i hear you. I'll post as much as I know shortly. Hope it will help.
As of now all I know is that this is used in an "Am/Fm Car Antenna", presumably to boost the signal like an LNA.

Do you have some lookup for analog IC's with marking codes ?