At an input voltages near mid-supply rails, their leakages are is pretty well matched, leaving only a small residual difference current of less than 1pA that appears as amplifier input bias current.
For any given unit, there is an input voltage where the input bias current is zero (assuming no significant package or circuit layout leakage). In fact, with a rail-to-rail op amp you can often self-bias the input (figure 2) and the output will drift to a voltage equal to the zero input bias current point. It’s an interesting experiment but not a particularly useful circuit.
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发表于 2024-11-4 11:28:34
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