| ??? 09/27/10 12:29 Read: times |
#178743 - 89S52 and BS170? |
Can someone please enlighten me why the BS170 FET pops instantly apon power-up, when the gate is driven from Port 2 via a 1K resistor? The load is an LED and it glows dimly on power-up. New working FET dead at this point.
The LED anode is connected to 9V via a 680ohm resistor, Cathode connected to the Drain of the BS170. The Source of the BS170 is connected to ground. Some of the BS170 circuits on the same port works flawlessly. Start-up code clears Port 2, and there is a logic 0 (0.023V actually) at the gate of the BS170. The 89S52 is fine but was changed anyway. Same problem. Tried increasing and decreasing the Gate resistor, same problem. Built the same circuit with an 89C2051, where it worked perfectly. The 89C2051 is capable of driving an LED directly and the 89S52 is not but since the FET is supposed to be Voltage dependant and not Current dependant like a transistor, this shouldn't matter. Eventually gave up with the BS170 and replaced the lot with BC517 darlington transistors. Project problem soved but I am still unaware of what I did wrong. |
| Topic | Author | Date |
| 89S52 and BS170? | 01/01/70 00:00 | |
| As written.... | 01/01/70 00:00 | |
| Exactly! | 01/01/70 00:00 | |
| almost true | 01/01/70 00:00 | |
| Series resistor to the gate | 01/01/70 00:00 | |
| Most 8051's | 01/01/70 00:00 | |
| Re: Most 8051's | 01/01/70 00:00 | |
| Several reasons... | 01/01/70 00:00 | |
| pop explained in earlier posts | 01/01/70 00:00 | |
| RE: pop explained in earlier posts | 01/01/70 00:00 | |
| RE: Several Reasons | 01/01/70 00:00 | |
| Update: May be ESD after all | 01/01/70 00:00 | |
| There is a trick... | 01/01/70 00:00 | |
RE: There is a trick... | 01/01/70 00:00 |