PASCO EM-8656 AC_DC ELECTRONICS LABORATORY - Manual (Page 124)

120
AC/DC Electronics Laboratory 012-05892A
®
Exp 9- Diodes
Analysis The diode acts as a one-way valve for electricity. Current
can flow in one direction, but not in the other.
Extensions
➀
A zener diode would be similar to the 4007, except
that there would be a breakdown point on the reverse
biasing, beyond which the current would flow. This
makes them useful for power regulation.
➁
) The LED opens up at a higher voltage than the 4007
(and it lights up).
Exp 10- Transistors
Analysis
➁
➂
The linear region does not include the origin, due to
the nonzero voltage that the junctions within the tran-
sistor require to turn on. (Similar to the effect in lab 9)
➃
Beyond the “saturation point”, the transistor is acting
like a short circuit. It offers no resistance to the cur-
rent; so beyond that point, there is no amplification.
The current is limited only by the battery and resistor.
➄
The current amplification of the transistor tested was
249. This value will vary from transistor to transistor;
it’s usually between 150 and 250 for the 2N3904 tran-
sistors supplied with the lab.
Discussion
➀ This graph shows the results of applying different val-
ues for R2. The amplification remains the same in
each linear region, but the size of that linear region
changes.
➁
The gain and/or saturation characteristics of the tran-
sistor will vary, although the basic shape of the graph
will remain the same.