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Electronics => Beginners => Topic started by: AlphZeta on February 13, 2012, 12:41:07 am

Title: Anyone knows this device?
Post by: AlphZeta on February 13, 2012, 12:41:07 am
Hi guys,

I have quite of few of this three-terminal devices (removed from satellite LNBF). Unfortunately I couldn't find the datasheet for it. If you take a look at the photo below, you will see that the device has the marking of SB2940G.

The table below lists the voltage drops among the pins when measured using the DMM diode range: (The device pins are 1, 2, 3 from left to right. The column represents the + lead and the row represents the - lead. So for instance, the voltage reading is 1.59 when the negative lead is connected to the middle pin and the positive lead is connected to the first pin). The voltage drop readings seem to be from two diodes connected in series but it doesn't look like a darlington though.

Any advice is greatly appreciated!

-+123
1-inf.inf.
21.59-1.59
31.79inf.inf.
Title: Re: Anyone knows this device?
Post by: klafaille on February 13, 2012, 01:30:40 am
The G suffix doesn't appear in it, but it's likely a flavor of voltage regulator as seen in the attached datasheet.
Title: Re: Anyone knows this device?
Post by: amyk on February 13, 2012, 10:26:05 am
The G suffix doesn't appear in it, but it's likely a flavor of voltage regulator as seen in the attached datasheet.
I agree with this. It's a Sino-Matrix SB2940 8.5V 350mA LDO: http://www.sinomatrix.com/eng/products.html (http://www.sinomatrix.com/eng/products.html)

The part number resemblance to the LM2940 is probably not coincidence.
Title: Re: Anyone knows this device?
Post by: AlphZeta on February 13, 2012, 02:22:02 pm
Thanks guys! I googled "SB2940" as well but nothing meaningful came back (SB2940 returns a bunch of non-related legislation stuff).  I will give it a shot.
Title: Re: Anyone knows this device?
Post by: DaveHardy on February 18, 2012, 02:03:30 am
Not a lot of beginners know this, but Japanese bipolar transistors are prefixed with a: 2SA, 2SB, 2SC or 2SD, and FET-s with 3S:
2SA - PNP, HF transistors,
2SB - PNP, LF transistors,
2SC - NPN, HF transistors,
2SD - NPN, HF transistors.

It doesn't work in this situation because the part has already been identified by a previous poster, but sometimes you can try 2SB2940 if you are looking for a cross.