Page 90 - Understanding Automotive Electronics

2735 | CH 3 Page 77 Tuesday, March 10, 1998 11:03 AM

ELECTRONICS FUNDAMENTALS 3

This is found by using the model and the equations V = i R , i = h i , and
c
c c
out
fe b
i = V /R , where h is the small signal current gain.
b
b
in
fe
Transistor amplifiers are Circuits such as those depicted in Figure 3.3 are combined to make many
commonly used in ana- types of amplifiers that are used in a variety of applications. Such circuits,
log circuits, including especially when made in one package with integrated circuit technology (to be
those in automotive sys- discussed later), are called linear circuits or analog circuits.
tems.
OPERATIONAL AMPLIFIERS
An op amp is a very high An operational amplifier (op amp) is another standard building block of
gain differential ampli- integrated circuits and has many applications in analog electronic systems. It is
fier. normally connected in a circuit with external circuit elements (e.g., resistors
and capacitors) that determine its operation. An op amp typically has a very
high voltage gain of 10,000 or more and has two inputs and one output (with
respect to ground), as shown in Figure 3.4a. A signal applied to the inverting
input (–) is amplified and inverted at the output. A signal applied to the
noninverting input (+) is amplified but is not inverted at the output.

Figure 3.4
Operational
Amplifier Circuit

FPO

UNDERSTANDING AUTOMOTIVE ELECTRONICS 77