Hello,
I've drawn a bit of a blank on this one: I am trying to identify a surface mount component.
SOT-23 (all three pins connected to PCB tracking).
Body marking: GS (the 'G' has a dot above it).
The lettering font is a bit weird. The 'G' could be a 9 and hence the body marking would be S9 (up-side-down GS if you understand my thinking here) or even 6S !
I am guessing it may be a Si Transistor.
Thanks for any help here,
Andy
I've drawn a bit of a blank on this one: I am trying to identify a surface mount component.
SOT-23 (all three pins connected to PCB tracking).
Body marking: GS (the 'G' has a dot above it).
The lettering font is a bit weird. The 'G' could be a 9 and hence the body marking would be S9 (up-side-down GS if you understand my thinking here) or even 6S !
I am guessing it may be a Si Transistor.
Thanks for any help here,
Andy
Probably it's an FET, with leads GDS, source as pin #1. The drain is #2, on the opposite side from pins 1 and 3.
yep, had previously tried all the on-line SMD codebooks, but upon investigating the suggested component datasheets, nothing really matches. What I want to see is a datasheet with that damn body marking explicitly stated. Yes, I can make an educated guess as to what it is, but the engineer part of me hates guessing!
Note: this is part of a reverse engineering project I am doing. Got all the surrounding circuitry mapped out so may post up a schematic of what I see.
Cheers chaps,
Andy
Note: this is part of a reverse engineering project I am doing. Got all the surrounding circuitry mapped out so may post up a schematic of what I see.
Cheers chaps,
Andy
You may not be able to determine the correct fet part number. Many smt parts are not marked, just no room.
explicitly stated yes, but no idea if it is the component
http://www.s-manuals.com/pdf/datasheet/j/1/j174-j177,_sst174-sst177_vishay.pdf
http://www.s-manuals.com/pdf/datasheet/j/1/j174-j177,_sst174-sst177_vishay.pdf
Circuit is part of a boiler controller. This part of the circuit generates an EHT spark to ignite the pilot flame & once lit, an ion detector to check for the presence of the flame once lit.
This is the (reverse engineered) schematic of surrounding circuitry of the 'mystery component':
Transistors etc are drawn as if the component is in it's package, as viewed from above.
Cheers,
Andy
This is the (reverse engineered) schematic of surrounding circuitry of the 'mystery component':
Transistors etc are drawn as if the component is in it's package, as viewed from above.
Cheers,
Andy
It must be an N-channel MOSFET.
The source is grounded, the gate is connected to R177, and the drain is connected to R190.
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That is the conclusion I immediately jumped to...
But!
Standard SMT pinout of an N-Chl Mosfet in SOT-23 package would indicate connection:
Gate = GND
Source = to base of transistor
Drain = R177
Hence for G & D one would expect them to be connected the other way around! This is why I am having difficulty id-ing this part. Maybe a JFet...?
Andy
But!
Standard SMT pinout of an N-Chl Mosfet in SOT-23 package would indicate connection:
Gate = GND
Source = to base of transistor
Drain = R177
Hence for G & D one would expect them to be connected the other way around! This is why I am having difficulty id-ing this part. Maybe a JFet...?
Andy
I agree a FET of some sort seems most likely. The 50 volt rating of C72 puts a limit on the current available via the two 1meg resistors.
I'm not well up on smd outlines, at least not from memory. Nothing FET like in that package/pinout configuration ? A JFET could be a possible because of its lower turn on volts compared to a normal FET... just looking at the likely voltages and all.
I'm not well up on smd outlines, at least not from memory. Nothing FET like in that package/pinout configuration ? A JFET could be a possible because of its lower turn on volts compared to a normal FET... just looking at the likely voltages and all.
Thanks. It was the pin outs I didn't know. JFET's I see typically have G in the middle so could be good. D and S are interchangeable in most true JFET's
I'm just thinking aloud...
Is the voltage on that resistor chain 'positive' ? If negative it could be a P channel. An N channel JFET would be on at 0 volts vgs and need negative voltage to turn it off whereas an ordinary vertical type would not. Vertical type would turn on with around 5 volts vgs. Can that much appear on the gate ? back to a P channel ???
Zebedee says
Is the voltage on that resistor chain 'positive' ? If negative it could be a P channel. An N channel JFET would be on at 0 volts vgs and need negative voltage to turn it off whereas an ordinary vertical type would not. Vertical type would turn on with around 5 volts vgs. Can that much appear on the gate ? back to a P channel ???
Zebedee says
GOTCHA!
MMBFJ113
http://www.farnell.com/datasheets/1727531.pdf
Body marking: 6S
Thanks all.
Interesting circuit t'boot.
MMBFJ113
http://www.farnell.com/datasheets/1727531.pdf
Body marking: 6S
Thanks all.
Interesting circuit t'boot.
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