TABLE OF CONTENTS Manufacturers sometimes (but not always) put switching time test results on their datasheets. Shown below are test circuits and test results for the 2N3904 NPN transistor. [6] From these test results we can approximate various charge control parameters.
Referring to Figure 10-9, the delay time listed ( t d = 35 nanoseconds) is the delay before the transistor turns on. The rise time ( t r) is the 10 90% risetime of the collector current. Storage time [7] ( t s) is the time it takes to remove saturation charge before coming out of saturation. The fall time t f is the time it takes collector current to fall from 90% of full value to 10%.
| SWITCHING CHARACTERISTICS | ||||||
|---|---|---|---|---|---|---|
| Delay Time | (V CC = 3.0 Vdc, V BE = 0.5 V dc, I C = 10 mAdc, I B1 = 1.0 mAdc) | t d | - | 35 | ns | |
| Rise Time | t r | - | 35 | ns | ||
| Storage Time
| (VCC = 3.0 Vdc, IC = 10 mAdc, I B1 = I B2 = 1.0 mAdc)
| 2N3903 | t s
| - | 175 | ns |
| 2N3904 |
- |
200 | ||||
| Fall Time | t f | - | 50 | ns |
