Electrical stimulation of neuromuscular tissues has been proven to treat many spinal cord injury-related clinical disorders, such as motor function restoration, epilepsy treatment, and other biomedical applications. Implantable electrical stimulators have emerged as promising solutions for long-term therapeutic and scientific biomedical purposes. However, designing such stimulators presents many challenges. This paper introduces an integrated circuit for an implantable electrical stimulator with high stimulation efficiency and a small on-chip area of 0.0833 mm 2. The device is capable of delivering a programmable stimulation current of up to 800 μ A to a load impedance of 2.5 k Ω while maintaining linearity. A power efficiency of 75.15% was achieved. The stimulator can deliver higher currents when connected to lower load impedances.