Another transistor question...

[Dave]

Anybody have any idea what the upper frequency limit is on a 2N2222?
Datasheet lists "typical freq (min)" as 200 MHz, but that's all. Any help
is appreciated...

Dave
db5151@hotmail.com

 

[Jamie]

the data book i use list transitors at their unity gain point.
meaning if a common emmitter amp would have a gain of lets say
200 at near 0 freq, at 200 mhz the gain will be 1
but that is how my manual spec's them.


Dave wrote:

Anybody have any idea what the upper frequency limit is on a 2N2222?
Datasheet lists "typical freq (min)" as 200 MHz, but that's all. Any help
is appreciated...

Dave
db5151@hotmail.com

 

[Watson A.Name - \"Watt Su]

"Dave" <db5151@hotmail.com> wrote in message
news:cje9e6$t4j@library2.airnews.net...

Anybody have any idea what the upper frequency limit is on a 2N2222?
Datasheet lists "typical freq (min)" as 200 MHz, but that's all. Any
help
is appreciated...

Depends on who made it. Like for TI for instance, the chip used in the
2N2222A (2N2222 is obsolete and hard to find, IIRC), is the N24 chip.
This is a 19 X 19 mil, epitaxial, direct-contact chip. The TI manual
says that it has a low of 100, typical 400 MHz, with test at 10V and 50
mA, 100 MHz. That sounds reasonable. But that's TI, and TI and
Motorola and a zillion other companies made 2N2222As, each maker having
made a different choice for the chip.

What datasheet were you referring to? What company? What date code?
Older ones could have a wider variation in Ft, so hand picking one could
result in a higher Ft.

Dave
db5151@hotmail.com

 

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[Tim Shoppa]

"Dave" <db5151@hotmail.com> wrote in message news:<cje9e6$t4j@library2.airnews.net>...

Anybody have any idea what the upper frequency limit is on a 2N2222?

Well, if you put 1GHz in you'll get *something* out... transistors
are usually specced by their "transition frequency" fT where AC small-signal-
current gain has declined to one. Generally fT has to be bigger than one if
you expect to get gain. fT itself is a function of several parameters
(notably collector current). And fT is usually implied by the gain-
bandwidth product at a frequency a few times lower than the measured fT
(with good reason, you usually want a gain of at least a few...)

If you're using the transistor as a saturating
switch then other parameters become more important, particularly base
capacitance. Many manufacturers publish "turn-off time" curves related
to this. In certain switch applications a jellybean NPN wouldn't be good
above a few MHz.

Datasheet lists "typical freq (min)" as 200 MHz, but that's all. Any help
is appreciated...

For current PN2222A parts, fT = 250MHz or 300MHz at collector current
of 20mA. It declines for both higher and lower currents. I don't know what
the original JAN specs said.

Tim.

 

[Watson A.Name - \"Watt Su]

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0409300154.588b1fbc@posting.google.com...

"Dave" <db5151@hotmail.com> wrote in message
news:<cje9e6$t4j@library2.airnews.net>...
Anybody have any idea what the upper frequency limit is on a 2N2222?

Well, if you put 1GHz in you'll get *something* out... transistors
are usually specced by their "transition frequency" fT where AC
small-signal-
current gain has declined to one. Generally fT has to be bigger than
one if
you expect to get gain. fT itself is a function of several parameters
(notably collector current). And fT is usually implied by the gain-
bandwidth product at a frequency a few times lower than the measured
fT
(with good reason, you usually want a gain of at least a few...)

If you're using the transistor as a saturating
switch then other parameters become more important, particularly base
capacitance. Many manufacturers publish "turn-off time" curves
related
to this. In certain switch applications a jellybean NPN wouldn't be
good
above a few MHz.

Datasheet lists "typical freq (min)" as 200 MHz, but that's all.
Any help
is appreciated...

For current PN2222A parts, fT = 250MHz or 300MHz at collector current
of 20mA. It declines for both higher and lower currents. I don't
know what
the original JAN specs said.

The specs aren't JAN, they're JEDEC. The PN2222A is the plastic cased
equival;ent of the 2N2222A.



> Tim.