Ge Transistor looks odd on component tester

[Flying]

I've just got 20 1T308B and they all display the diode symbol between the collector and emitter with a forward voltage around 4v on my component tester. I'm new to Ge transistors so it could well be normal for them, but if anyone can shed some light on what it means I would be grateful.

My plan is to use them in a Fuzz Face, but I'm not convinced they will be any good, but haven't breadboarded a FF to try them in yet.

 

[fig]

I think it's giving you the measurement between the emitter and collector, which would form a 3rd diode to the component.

BJTs are really just 2 connected diodes. When the cathodes join, it's a PNP (positive/anode to negative/cathode--cathode/negative to anode/postive), when the anodes join, it's a NPN.

 

[Flying]

Hi Fig, the odd thing is that it is only this batch of transistors, I've never tested a transistor and had it show a diode between the Emitter and Collector. before The leakage looks fine at 11 microamps (assuming ICEO can be used as a rough leakage measurement), but I just feel something is wrong.

For example if I put this into a fuzz face and bias T2 to 4.5-5v that's over the forward voltage threshold of the 'diode' between the collector and emitter... I think... actually I'm out of my depth and just confused

 

[peccary]

I remembered seeing that symbol in the DCA 75 user manual, so I went back to look at it and saw it listed as a "free wheeling diode," which is apparently just a protection diode within the transistor.

That symbol appears on page 19 in the user guide: https://www.peakelec.co.uk/downloads/dca-pro-user-guide-en.pdf

 

[fig]

those free-wheelin diodes are always doing doughnuts in my yard.

Thanks Joe. I'm getting a division by zero now.

I think... actually I'm out of my depth and just confused

When did you discover your ability to read minds?

 

[peccary]

those free-wheelin diodes are always doing doughnuts in my yard.

Thanks Joe. I'm getting a division by zero now.

When did you discover your ability to read minds?

 

[Flying]

Thank you both. So essentially nothing to worry about?

 

[fig]

No, I wouldn't think so. socket it and rock it..it

 

[Chuck D. Bones]

I remembered seeing that symbol in the DCA 75 user manual, so I went back to look at it and saw it listed as a "free wheeling diode," which is apparently just a protection diode within the transistor.

That symbol appears on page 19 in the user guide: https://www.peakelec.co.uk/downloads/dca-pro-user-guide-en.pdf

The only transistors I've seen with free-wheeling diodes in them are high power devices. Sometimes these cheap little testers get confused. When I get screwy data from my tester, I take the device out, turn it around and try again. Like Fig said, it should work so Rock On!

 

[peccary]

The only transistors I've seen with free-wheeling diodes in them are high power devices. Sometimes these cheap little testers get confused. When I get screwy data from my tester, I take the device out, turn it around and try again. Like Fig said, it should work so Rock On!

Hey, at least I read the manual!

 

[PJS]

The only transistors I've seen with free-wheeling diodes in them are high power devices. Sometimes these cheap little testers get confused. When I get screwy data from my tester, I take the device out, turn it around and try again. Like Fig said, it should work so Rock On!

The 2n7000 FETs in the OCD have protection diodes - it is these diodes that actually do the clipping - nothing to do with the actual FET

 

[Chuck D. Bones]

I should have said "The only bipolar transistors I've seen with free-wheeling diodes..."
Low power MOSFETs like the 2N7000 & BS170 contain body diodes just like their big brothers that are a consequence of the manufacturing process. And yes, for some reason pedal designers like using the body diodes in MOSFETs for clipping diodes. When I was designing switching power supplies and Class-D amplifiers, we wished the body diodes did not exist in high-power MOSFETs because they created more problems than they solved.