| Electronics > Beginners |
| constant current source design |
| << < (6/6) |
| Jay_Diddy_B:
Hi Tom45 and the group, The Vbe of the transistor has a temperature coefficient of -2mV per degree C. The current will rise by about 2mV / Re, where Re is the emitter resistor. Regards, Jay_Diddy_B |
| Arjunan M R:
--- Quote from: Tom45 on June 04, 2019, 07:47:49 pm ---Since you don't need much accuracy, why not just use a simple 1 transistor current sink. The circuit below uses a 2N3904 and 3 resistors. Testing shows that it works down to 0.2 volts. Current was about 1 ma at 0.2 volts, up to about 1.2 ma at 25 volts. If you don't have 5 volts available, just recompute the base bias resistor divider for whatever voltage you do have. --- End quote --- NO I'm not using this circuit.Since I have to make the BOM as low as possible I will go with the other. I'm not going to buy three different types of resistors. In the other I only have to buy one type of resitor extra.49.9 \$\Omega\$\$\Omega\$.I already need 4K7. Thanks for reply. |
| Arjunan M R:
I don't need accuracy but the current has to constant as possible. Because I'm using an 18 bit ADC to measure current . I don't want to zero it out whenever i change the voltage. |
| Navigation |
| Message Index |
| Previous page |