| ??? 05/09/08 14:26 Read: times |
#154622 - Exactly! Responding to: ???'s previous message |
Suresh, you don't need the exact number of hfe. For fully turning on the transistor you will need to drive the base with a current that is about Icmax / 10 anyway. You will quickly see, that a rather high base current is needed, which in turn needs an additional driver to drive the base. It's not unusual resulting in a cascode circuit of three or even more transistors (like Darlington, for instance) only to be able to source/sink the motor current.
Don't forget, the hfe graph is only typical data. There's no discrepancy in the datasheet. As Oliver already mentioned, measure the DC resistance of your (unconnected!) motor and you have the maximum current. By the way, I think the transistor is a bit too weak to properly drive your motor... Kai |
| Topic | Author | Date |
| Clarification on choosing Hfe | 01/01/70 00:00 | |
| search again | 01/01/70 00:00 | |
| Its max current is 0.6A | 01/01/70 00:00 | |
| so if You continue playing .. | 01/01/70 00:00 | |
| My doubt is only on choosing Hfe.. | 01/01/70 00:00 | |
| read again | 01/01/70 00:00 | |
| Any hfe will work | 01/01/70 00:00 | |
| Exactly! | 01/01/70 00:00 | |
| How driving it? PWM or ON/OFF? | 01/01/70 00:00 | |
| PWM and ON/OFF | 01/01/70 00:00 | |
| Use a MOSFET | 01/01/70 00:00 | |
| See the typical transistor curves | 01/01/70 00:00 | |
| Here comes the spoon... | 01/01/70 00:00 | |
| You replies are clear.. | 01/01/70 00:00 | |
| Higher heat dissipation | 01/01/70 00:00 | |
Thank You! | 01/01/70 00:00 |