On Wed, 24 Oct 2012 16:44:06 -0400, Spehro Pefhany
On Wed, 24 Oct 2012 16:27:02 -0400, Roberto Waltman
Spehro Pefhany wrote:
On Wed, 24 Oct 2012 15:27:12 -0400, Roberto Waltman
John Larkin wrote:
...
This is my first-pass qualifier question.
+10V
|
|
C
+5V--------------B
E
|
1K
|
gnd
(drawn like a real schematic, on a whiteboard)
What is the base voltage? (one answer: 0.6!)
What is the emitter voltage?
What is the collector voltage?
What is the base current?
What is the emitter current?
What is the collector current?
Any other comments?
Germanium or silicon?
PNP or NPN?
Roberto Waltman
[Running for cover...]
For a (slightly) more advanced test..
-10V
|
1K
|
C
-5V--------------B NPN
E
|
gnd
One more question: What is the pressure of the magic smoke inside the
transistor?
If it's a jellybean NPN, the E-B junction is going to be just fine
(typically they break down around 8-9V and are rated for at least 5V),
and the answers are, as JL says, going to be about the same as his
example except for the higher base current due to typically low
reverse beta. But it fits a different visual pattern, being an NPN
with E grounded-- it's probably not obvious that it's a
"collector-follower".
That's way overkill for a first question interview. If some kid
doesn't know about reverse beta, I wouldn't chuck him out right away.
I measured a BFT25 as having reverse beta about 4.