Tab Electronics Guide to Understanding Electricity ... - Sciences Club

Transistors
193
As you have seen, these basic operational characteristics of transistors
can be manipulated into providing DC voltage amplification, AC voltage
amplification, current regulation, voltage regulation, current limiting,
and beta enhancement (i.e., Darlington pairs). These basic fundamental
building blocks of transistor applications can be combined in various
ways to provide a large variety of more complex functions and circuitry.
All of the circuits in this transistor workshop section have incorporated
NPN transistors. PNP transistors can be used in the identical
manner if all of the circuit voltage polarities are reversed.
Throughout this book, I specify the “typical” forward threshold voltage
of any forward-biased semiconductor junction as 0.7 volt. You may
want to keep in mind that it is a little more technically accurate to consider
this voltage to be 0.68 volt (i.e., 0.68 volt will be a little more accurate
in the majority of cases). I elected to approximate this voltage at 0.7 volt
for ease of calculation.
If this is your first reading of this section, I recommend that you
now go back to the beginning of this chapter and study the entire contents
up to this point again. The information contained in this chapter
is concentrated and quite abstract to most individuals on their first
exposure to it. Don’t become disheartened if you are confused on some
points. Most of these fundamentals will become clearer during your
second study, and most of your questions will probably be answered in
later chapters.
Assembly and Testing of Last
Section of a Lab Power Supply
The following materials are needed to complete this section:
Quantity Schematic Reference Item Description
6 D1 through D6 1N4001 (NTE 116) general-purpose silicon diode
2 R1 and R2 1000-ohm, 2-watt resistor
2 R3 and R4 2.2-Kohm, 2-watt resistor
2 R7 and R8 470-ohm, 1 2 -watt resistor
2 R5 and R6 0.4-ohm, 5-watt resistor
2 P1 and P2 1000-ohm, linear taper 2-watt potentiometer
2 C3 and C4 0.1-F ceramic disk capacitor
2 Q3 and Q5 TIP 31C (NTE 291) transistor
2 Q4 and Q6 TIP 32C (NTE 292) transistor
1 Q1 2SC3281 (NTE 2328) transistor