This chapter explores electrical stimulation of excitable biological
entities. It provides a brief history of electrical stimulation, stimulation
parameters, theory of electrode interface impedance, and types of
stimulation. Focus is on the technology of charge balancing, power losses,
voltage compliance, and associated hardware complexities of electrical
stimulators. Stimulus artifacts and inductive power delivery are also
discussed, and are often used with stimulators for applications in neural
prostheses and therapeutics [1, 2].
Introduction
Electrical stimulation is an important and popular method in which injected
charges are mainly responsible for excitation or inhibition of neural or
motor structures [3–5]. It can be utilized for treatment of diseases
and restoration of dysfunctional organs, such as for the brain [6, 7],
retina [8, 9], cochlea [10], or peripheral nerve [11]. The electrical
stimulation process is accomplished by using conductive electrodes of
specific size and shape, which are placed at desired biological sites of
interest. Coulombic charge is injected through such electrodes by means of
constant current or constant voltage pulses. Charge injection accuracy,
power loss minimization, output voltage compliance, and miniaturization are
important factors that can enhance practical performance in electronic
stimulators [12]. In the following subsections we provide a brief history
and introduce technical parameters associated with electrical
stimulation.