Transistor question

D

Dave

Guest
Was trying to test a 2N3906 (PNP 2N2222 substitute) and found something
strange. My DMM has a transistor built into it with a socket marked EBCE
and I wasn't sure which configuration the transistor had. When plugging
what should be the emitter/base/collector into the appropriate slots, it
came up with an hfe reading of 150, which is a little low but in the
ballpark. But if I move it down one slot and plug what should be the
collector into the bottom emitter slot/base into the collector slot/emitter
into the base slot, the hfe reads 1500! Anybody have any idea what gives
with this? Is it possible that the transistor has two operable
configurations? Or do I have a faulty tester built into my DMM?

Crossposted to sci.electronics.equipment, just in case

Thanks much,

Dave
db5151@hotmail.com
 
150 is more like it.


Dave wrote:

Was trying to test a 2N3906 (PNP 2N2222 substitute) and found something
strange. My DMM has a transistor built into it with a socket marked EBCE
and I wasn't sure which configuration the transistor had. When plugging
what should be the emitter/base/collector into the appropriate slots, it
came up with an hfe reading of 150, which is a little low but in the
ballpark. But if I move it down one slot and plug what should be the
collector into the bottom emitter slot/base into the collector slot/emitter
into the base slot, the hfe reads 1500! Anybody have any idea what gives
with this? Is it possible that the transistor has two operable
configurations? Or do I have a faulty tester built into my DMM?

Crossposted to sci.electronics.equipment, just in case

Thanks much,

Dave
db5151@hotmail.com
Click to expand...
 
"Norm Dresner" <ndrez@att.net> wrote in message
news:f2F6d.455795$OB3.172167@bgtnsc05-news.ops.worldnet.att.net...
"Dave" <db5151@hotmail.com> wrote in message
news:cjf2a1$mja@library2.airnews.net...
Hmm. Okay. Makes more sense than anything I can think of. My wife
says
that 20 years ago I told her about this effect and explained it. Only,
that
was 20 years ago. :)


She remembered and you didn't. What does that tell you about memory and
aging and gender?
Click to expand...
YEAH! And testosterone and Estrogen. It's not fair...

(But what is?)

Dave
db5151@hotmail.com
 
Oh yeah, no doubt. I am just trying to figure out why I got an hfe reading
of 1500 with the transistor basically reversed. Any ideas on that?

Thanks,

Dave
db5151@hotmail.com

"Jamie" <jamie_5_not_valid_after_5_Please@charter.net> wrote in message
news:10llg4enpn6la30@corp.supernews.com...
150 is more like it.


Dave wrote:

Was trying to test a 2N3906 (PNP 2N2222 substitute) and found something
strange. My DMM has a transistor built into it with a socket marked
EBCE
and I wasn't sure which configuration the transistor had. When plugging
what should be the emitter/base/collector into the appropriate slots, it
came up with an hfe reading of 150, which is a little low but in the
ballpark. But if I move it down one slot and plug what should be the
collector into the bottom emitter slot/base into the collector
slot/emitter
into the base slot, the hfe reads 1500! Anybody have any idea what
gives
with this? Is it possible that the transistor has two operable
configurations? Or do I have a faulty tester built into my DMM?

Crossposted to sci.electronics.equipment, just in case

Thanks much,

Dave
db5151@hotmail.com
Click to expand...
 
Hmm. Okay. Makes more sense than anything I can think of. My wife says
that 20 years ago I told her about this effect and explained it. Only, that
was 20 years ago. :)

Thanks for the feedback. It is appreciated.

Dave
db5151@hotmail.com

"Jamie" <jamie_5_not_valid_after_5_Please@charter.net> wrote in message
news:10llr7bi1vnjua8@corp.supernews.com...
short effects due to improper polarity throwing off your meter.
if you put the vcc in the Base the emitter will sure get a lot for
output with no current on the base leg.
this will give the illusion of high gain.


Dave wrote:

Oh yeah, no doubt. I am just trying to figure out why I got an hfe
reading
of 1500 with the transistor basically reversed. Any ideas on that?

Thanks,

Dave
db5151@hotmail.com

"Jamie" <jamie_5_not_valid_after_5_Please@charter.net> wrote in message
news:10llg4enpn6la30@corp.supernews.com...

150 is more like it.


Dave wrote:


Was trying to test a 2N3906 (PNP 2N2222 substitute) and found something
strange. My DMM has a transistor built into it with a socket marked

EBCE

and I wasn't sure which configuration the transistor had. When
plugging
what should be the emitter/base/collector into the appropriate slots,
it
came up with an hfe reading of 150, which is a little low but in the
ballpark. But if I move it down one slot and plug what should be the
collector into the bottom emitter slot/base into the collector

slot/emitter

into the base slot, the hfe reads 1500! Anybody have any idea what

gives

with this? Is it possible that the transistor has two operable
configurations? Or do I have a faulty tester built into my DMM?

Crossposted to sci.electronics.equipment, just in case

Thanks much,

Dave
db5151@hotmail.com
Click to expand...
 
"Dave" <db5151@hotmail.com> wrote in message
news:cjf2a1$mja@library2.airnews.net...
Hmm. Okay. Makes more sense than anything I can think of. My wife says
that 20 years ago I told her about this effect and explained it. Only,
that
was 20 years ago. :)
Click to expand...
She remembered and you didn't. What does that tell you about memory and
aging and gender?
 
short effects due to improper polarity throwing off your meter.
if you put the vcc in the Base the emitter will sure get a lot for
output with no current on the base leg.
this will give the illusion of high gain.


Dave wrote:

Oh yeah, no doubt. I am just trying to figure out why I got an hfe reading
of 1500 with the transistor basically reversed. Any ideas on that?

Thanks,

Dave
db5151@hotmail.com

"Jamie" <jamie_5_not_valid_after_5_Please@charter.net> wrote in message
news:10llg4enpn6la30@corp.supernews.com...

150 is more like it.


Dave wrote:


Was trying to test a 2N3906 (PNP 2N2222 substitute) and found something
strange. My DMM has a transistor built into it with a socket marked

EBCE

and I wasn't sure which configuration the transistor had. When plugging
what should be the emitter/base/collector into the appropriate slots, it
came up with an hfe reading of 150, which is a little low but in the
ballpark. But if I move it down one slot and plug what should be the
collector into the bottom emitter slot/base into the collector

slot/emitter

into the base slot, the hfe reads 1500! Anybody have any idea what

gives

with this? Is it possible that the transistor has two operable
configurations? Or do I have a faulty tester built into my DMM?

Crossposted to sci.electronics.equipment, just in case

Thanks much,

Dave
db5151@hotmail.com
Click to expand...
 
"Dave" <db5151@hotmail.com> a écrit dans le message news:
cje99p$61@library2.airnews.net...
Was trying to test a 2N3906 (PNP 2N2222 substitute) and found something
strange. My DMM has a transistor built into it with a socket marked EBCE
Click to expand...
Hi Dave
The transistor tester is made of a known current generator, connected to the
base.
Emitter is grounded.
Collector has a voltage generator, probably a resistor to limit the current, and
a current measure.

If you shift the plugs, you connect E to the base generator, B to collector, and
C to ground. So, the current generator is ignored because reverse biased. The
collector/base junction of the tested transistor has, in serie, the voltage
generator, the milliameter and the protective resistor, direct biased. The
current is MAXIMUM limited by R. Usually, the indication is overflow (no value),
but on your DMM it is the same as the current for hfe 1500.

--
Guy Pastuzak

Adresse ANTISPAM
ANTISPAM address
 
<< I am just trying to figure out why I got an hfe reading
of 1500 with the transistor basically reversed. Any ideas on that? >>

Dave-

As others have pointed out, you may not have it exactly reversed. Finite
output divided by zero input equals infinite apparent gain!

If you did have the transistor connected with collector and emitter reversed,
it should still function as a transistor, but most likely would have much lower
gain. You would also expect it to have a lower breakdown voltage.

At one time in the development of computer circuits, a transistor was designed
and produced that was somewhat symmetrical. According to its specifications,
it worked equally well connected either way. I do not recall a specific part
number or the circuit in which it was used. This was probably around 40 years
ago.

Fred
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top