I have a circuit where I sense an input which is a voltage divider with resistor.
Since the voltage divider needs to have high impedance, the current flowing through is in the range of 10's of uA.
I need to protect the the analog input so that the voltage doesn't exceed 5V. Maximum range is 200mV (so clamping anywhere between 250mV to 5V is acceptable).
The first choice would be a Zener diode, but the problem is the reverse leakage current of those starts at in the 1uA range, which would induce an error to the measurement.
Maximum allowable current leakage is 25nA.
I thought of using a regular diode in forward mode but they also leak below the conductive threshold.
Is there any other clever way to clamp over voltage while having minimum leakage current ?
Is this solution a viable idea ? Transistor have a CE leakage in the nA range, cascading 2 allows to increase the voltage.
The simulation give a leakage current of 14pA at 200mV at the resistor node.