Chargebalanced

Chargebalanced refers to a property of electrical signals, stimulation protocols, or systems in which the net injected electrical charge over a defined period is zero. This balance is most commonly sought in biomedical electrical stimulation to avoid accumulation of charge at the electrode–tissue interface, which can cause tissue damage or electrode degradation.

In practice, chargebalanced stimulation is often achieved with biphasic pulses that consist of two phases with opposite polarity. The areas under the current–time curves for the two phases are designed to be equal, ensuring zero net charge per pulse. The balance can be implemented with symmetric, or carefully designed asymmetric, waveforms and may use either passive discharge paths or active current steering to maintain balance across cycles.

The purpose of ensuring charge balance is to prevent DC offset and minimize electrode polarization, which can alter impedance, reduce safety margins, and shorten device life. This is a central consideration in implanted neural stimulators, such as cochlear implants, deep brain stimulators, and retinal prostheses, as well as in transcutaneous stimulation systems used for therapy or research.

Challenges in achieving and maintaining chargebalance include electrode-tissue interface dynamics, changes in impedance over time, and delays or mismatches between phases. Practical designs must account for these factors to maintain true balance across operating conditions. Ongoing monitoring and calibration, along with robust current sources and safety limits, help ensure that charge balance is preserved during use.

See also: charge balance, biphasic stimulation, neural stimulation safety, electrode impedance.