Transistors: NPN - Collector as input base as output?

[ngmedaboard]

Hi, I'm an experienced EE but don't touch BJT's all that often. In any case to cut to the chase, I've encountered a circuit that appears to use the collector of an NPN as it's input per say, with the base as its output. I suspect this somehow can regulate how much current is pulled by the base but it isn't entirely clear. I've drawn this schematic from an actual circuit. I've triple checked the data sheet for the transistor, because I think the Base and Collector look backwards to me. While listed as an MMBT6429LT1, the transistor is currently a 2N3901 (went end of life a while ago). The circuit works.

**broken link removed**

If anyone could shed some light on this; confirm this is a valid circuit and give a brief theory of operation it would be greatly appreciated.

Thanks,

-NGM

 

[IanP]

No, mate, this circuit can only work when the Collector is connected to R1/R3 and the Base is fed from 555-timer ..
Your drawing is incorrect ..

Keep in mind, there are three pin allocations for small-signal transistors:
- American: e-b-c
- Japanese: e-c-b
- European: c-b-e

Rgds,
IanP

 

[ngmedaboard]

Ok, you make me feel a little better as I was beginning to question my basic understanding of electronics, haha. The signal is clearly entering via the 2nd pin or the center pin. This meshes properly with your TO-92 package conventions for American transistors with the base in the center.

Now take a look at this datasheet for the 2N3901 that calls out the CZ pin arrangement and you'll see it calls it out otherwise.

Is it possible the 2N3901 was available with different pin outs?

Any thoughts?

 

[erikl]

Any thoughts?

Stamp really well legible? Or could it be a 2N3904 ?

 

[FvM]

There have been "american" transistors with different pinout, don't remember the types. But rather than guessing about the transistor,
the doubts can be cleared in a few seconds with a multimeter.