... with requirements as clear as mud and no context.:roll:strange project, my friend
A logarithmic scale may be more useful. The current could be passed through a diode, and the voltage drop across the diode sensed with a suitable opamp. CMOS opamps are available with bias currents less than 1pA.I guess your scale is too big.... 10pA -10mA
It's easy. Refer to the circuit from post #10, calculate a suitable feedback resistor value (500 Meg), change 741 against an "electrometer" OP with sub pA input current (e.g. OPA129) and you're done.Can you help me in designing a circuit for shorter range?