TABLE OF CONTENTS Resistors are ubiquitous. Because of this their performance is taken for granted; provided they are operated within their power, voltage and environmental ratings this is reasonable, since after millions of accumulated resistor-years experience there is little left for their manufacturers to discover. But there are still applications where specifying and applying resistors needs to be handled with some care.
Let us start with an appreciation of the different varieties of resistor that are available. Table 3.1 (opposite) is a guide to the common types that will be encountered in general circuit design. There are more esoteric types which are not covered.
| Type | Ohmic Range | Power range | Tolerance | Tempco range | Manufacturers | Applications | Cost |
|---|---|---|---|---|---|---|---|
| Carbon film | 2.2 - 10M | 0.25 - 2W | 5% | -150 > -1000ppm/ C | Neohm, Rohm, Piher | General purpose/ commercial | < 1p |
| Carbon composition | 2.2 -10M | 0.25 - 1.0W | 10% | +400 > -900ppm/ C | Neohm, VTM, Welwyn | Pulse, low inductance | |
| Metal film (standard) | 1 - 10M | 0.125 - 2.5W | 1%, 2%, 5% | +/-50 > 200ppm/ C | BC, Neohm, Vishay, Piher, Rohm, Welwyn | General purpose industrial & military | 1 - 3p |
| Metal film (high ohm) | 1M - 100M | 0.5 - 1W | 5.00% | +/-200 > 300ppm/ C | BC, Neohm | High voltage & special | 5 - 20p |
| Metal glaze | 1 ? 100M |
