Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.
Sign up to join this community
Hello,
I have a question, If my circuit will work:
Function: Gate is on GND Supplying a voltage betwenn 0V and 10V 10V Input is ~3.3V output If the voltage goes above 10V the diodes D2 and D3 clamp it to ~3,3V (This works as I understand)
Function Vgate = 3.3v Supplying a current between 0mA to 20mA the voltage drop at R3 should "Supply" the voltage divider again max output is 3.3V
Will the 2nd function work?
The Si2356 is a good choice for a 3.3 volt gate control. It will have an on-resistance of about 0.05 ohms and that is negligible compared to the 499 ohm resistor (R3) so 20 mA will produce 9.98 volts across R3. The impact of 150 k in parallel with R3 is also quite negligible (it'll drop to 497.3 ohms) so the real voltage developed for 20 mA is 9.95 volts.
When using it as a voltage potential divider there will be anything from 1 uA to 10 uA leakage into the "off" MOSFET but, in comparison with the current though the series combo of R1 and R2 isn't a big deal.
R1 and R2 convert 10 volts to 3.329 volts but beware of resistor tolerances. For instance, if using 1% resistors for R1 and R2, 10 volts in could mean the 3.329 volts is a bit higher at nearly 3.4 volts. I don't think it'll cause a problem other than the uncertainty of value. I'd use 0.1% resistors if it is critical for performance.
Your current source, I1, is probably upside down.
At 20 mA there will be 10 V across R3. If Q1 is off then the voltage at the top of R3 will rise to its maximum possible.
The 100k and the diodes will still protect the output.
I recommend that you turn off the grid when taking screenshots. This will improve legibility.
