| ??? 05/01/09 12:44 Modified: 05/01/09 12:46 Read: times |
#164986 - Check values Responding to: ???'s previous message |
Check the component values in this circuit- with R3=15R the current through Q1 will be (5-1.2)/15 which is 253mA. The 2N3906 is rated at maximum 200mA Ic. It also makes R3 a 1W resistor and even then it will be really hot!
Also 4mA base current with a worst case gain of 100 is probably not enough guarantee saturation of Q1 with that kind of collector current. -Aubrey |
| Topic | Author | Date |
| Driving TIP120 from 8052 | 01/01/70 00:00 | |
| It is the Current | 01/01/70 00:00 | |
| Use this type circuit | 01/01/70 00:00 | |
| Thanks, I'll give it a try | 01/01/70 00:00 | |
| 0.1A | 01/01/70 00:00 | |
| Michael circuit is fine with some diff values. | 01/01/70 00:00 | |
| Success! | 01/01/70 00:00 | |
You use a Darlington, ... | 01/01/70 00:00 | |
| Check values | 01/01/70 00:00 | |
| is Q2 not a bit overkill? | 01/01/70 00:00 | |
| Base current and transistor beta | 01/01/70 00:00 | |
| logic level MOSFET | 01/01/70 00:00 | |
| they do make p-channel logic mosfets | 01/01/70 00:00 |