markbng
Junior Member level 1
Hi,
I want to make an auto ranging uCurrent. The measured current goes through a 10 mOhm, 10 Ohm or 10k resistor. I want to be able to switch between these measurement resistor branches with a switching N-fet or something. so all these resistors are connected with each other in 1 point and the other end goes to the drain of a N-Fet. all source connections are connected to ground. The source of the selected measurement resistor value has a high voltage to enable this resistor. But my problem is the 10k range. This measures nA (10e-9). if other branches leak nA, then I have a problem. What FET can I use that has a low capacitance and very high impedance (GOhm)? Or do you have another solution. How can I switch between the measurement resistors? I will probably change the FET in the design. First the FET and than the measurement resistor to ground. Can someone help me in this part of the design. I want to measure nA, so only a leakage of a couple of pA is exeptable. Any help is appreciated.
Kind regards,
Mark
I want to make an auto ranging uCurrent. The measured current goes through a 10 mOhm, 10 Ohm or 10k resistor. I want to be able to switch between these measurement resistor branches with a switching N-fet or something. so all these resistors are connected with each other in 1 point and the other end goes to the drain of a N-Fet. all source connections are connected to ground. The source of the selected measurement resistor value has a high voltage to enable this resistor. But my problem is the 10k range. This measures nA (10e-9). if other branches leak nA, then I have a problem. What FET can I use that has a low capacitance and very high impedance (GOhm)? Or do you have another solution. How can I switch between the measurement resistors? I will probably change the FET in the design. First the FET and than the measurement resistor to ground. Can someone help me in this part of the design. I want to measure nA, so only a leakage of a couple of pA is exeptable. Any help is appreciated.
Kind regards,
Mark