1.3 BASIC NOTES ABOUT CHIPS
• The cases come in many forms, but for inhouse development the DIP (Dual In-Line Pin) package is most popular, and most chips here are numbered with the same pin convention, unless specified.
• Chips are labelled with part numbers, for example the 74F147, will logically be equivalent to the 74LS147, except that they will have different rated speeds. The ‘F’ signifies fast, and ‘LS’ signifies low speed.
• There are extensive volumes of databooks available for chips, these are typically low cost, and available at any vendor of microchips.
• Many manufacturers make common chips, with the same IC numbers. But, there are also many proprietary chips. Be wary when selecting a non-standard IC, small purchases may be frowned upon by the supplier, making them hard to get in quantities of less than 1000.
• Some IC manufacturers are,
- National Semiconductor
- Texas Instruments
• CMOS chips will need pull-up resistors on inputs.
• When TTL inputs have nothing attached they tend to “float high” and will indicate that an input is true.
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