Transistor Specification Selection Guide
Operating Voltage Range
| Bipolar Transistors
Field Effect Transistors
- Power supply voltage for best operation.
- needs to fit application.
- Battery operated applications require low voltages, depending on the number of cells used. A single cell lithium battery provides approximately 1V when regulated, degrading to about 0.9 at end of life. Pagers typically use a single cell; PCS and cordless phones often use 3 cells; many cellular phones and portable LANs use a 5 or 6 cell design. Applications that "plug in" to a power grid typically have fewer power supply constraints than battery operated systems; 12, 15 and 24 V rails are commonly available in such systems.
- The operating voltage of a BJT is limited on the low end by the turn-on voltage, which depends largely on epitaxial material properties. The high end is limited by breakdown voltages, also a strong function of epi;. A good rule of thumb is to operate at least a volt below the BVceo value listed in the Maximum Ratings table on the data sheet for linear (class A) operation, and below 1/2 the BVcbo value for class C (large signal) use.
- Most AT series bipolars have an operating voltage range of 1-10 volts.
- The AT-3x family is designed specifically for battery operation, and has a range of 0.3 - 6 V.
- The AT-3x power devices can operate at 3.6, 4.8, or 6 V.
- The AT-640 family uses a power process, and can operate up to 18 V.
- FETs are designed to operate at lower voltages than bipolars. Their operating range is determined by breakdown voltages, which depend on process.
- Most small signal FETs operate well in the 1 - 3 volt range.
- PHEMTs operate at slightly lower voltages (0.5 - 2 V).
- Power FETs operate up to 9 V