CHAPTER 15 ■ COMPARATORSThe letter ”N” follows each part number in Table 15-1. The final letter(s) in a part number usually
signify the chip’s package size, package material, and/or temperature tolerance. For parts manufactured by
National Semiconductor, the letter “N” represents a dual inline package, otherwise known as a DIP.
If you mistakenly purchase an LM393M (“M” not “N”) chip, you’ll find it encased in a different package.
The SO-8 or SOIC narrow package won’t fit into the solderless breadboard (see Figure 15-4).
Table 15-1. Dual Comparators
Supplier Part Number Price
Mouser 512-LM393N $0.44
Mouser 863-LM2903NG $0.44
Jameco 24281 $0.25
Digi-Key LM393NGOS $0.45
Digi-Key LM2903NGOS $0.44
Figure 15-4. LM393N is DIP (left), LM393M is SOIC narrow (right)
Brightness Comparator Circuit
The brightness comparator circuit connects to the balanced brightness-sensing circuit from the prior
chapter. This is the brain that reads the photoresistor sensors and then controls the motors accordingly.
Comparing a Schematic with a Wiring Diagram
Instead of a formal schematic, the brightness comparator circuit is presented as a wiring diagram
in Figure 15-5.