Figure 3-35. RTL integrated circuits.
DTL (DIODE TRANSISTOR LOGIC)
Input signals are applied to diodes in this logic family. The diodes either conduct or cut off and
produce the desired output from the transistor. DTL is normally found in dual-inline packages (DIP) as
well as older discrete component logic.
TTL (TRANSISTOR-TRANSISTOR LOGIC)
In TTL, transistors with multiple emitters are used for the logic inputs. Additional transistors are
used to produce the desired output. TTL is normally packed in DIPs and is quite common in military
CMOS (COMPLEMENTARY METAL OXIDE SEMICONDUCTORS)
The CMOS logic circuits use metal oxide semiconductors similar to field-effect transistors (FETs).
LOGIC FAMILY USE
The logic family used in a piece of equipment is determined by the design engineers. The type of
logic used will be based on the requirements of the equipment and on what family best fulfills the
The use of integrated circuits enables designers to produce equipment that is very small and highly
efficient when compared to other methods of construction. The block diagram shown in figure 3-36, view
A, represents an 8-bit, serial-input and parallel-output shift register. This circuit is contained in a standard
14-pin DIP measuring about 0.75 inch long and 0.25 inch wide. View B shows this circuit package.