Disclosed are systems, apparatus, and methods for sensing currents conducted via an electrode. In various embodiments, an apparatus may include an operational amplifier including a first input terminal, a second input terminal, and an output terminal. The first input terminal may be configured to electrically couple with the electrode. The apparatus may further include a feedback circuit coupling the output terminal of the operational amplifier to the first input terminal. The feedback circuit may comprise a plurality of transistor devices configured to generate a feedback current based on a voltage value of the output terminal. The plurality of transistors may be further configured to provide the feedback current to the first input terminal. The apparatus may also include a voltage source coupled to the second input terminal and configured to maintain a substantially constant voltage at the second input terminal.