Design and Construction of a Simple Heartbeat Signal Amplifier Circuit Based on AD8232

Cardiovascular activity monitoring relies heavily on accurate Electrocardiogram (ECG) signal acquisition, which is often challenged by low signal amplitudes (1 mV) and ambient electrical interference. This study presents the design, hardware implementation, and performance characterization of a compact, cost-effective biopotential signal conditioning circuit based on the AD8232 front-end IC. Utilizing a Research and Development (R&D) framework, the proposed system integrates an instrumentation amplifier, active High-Pass (HPF) and Low-Pass (LPF) filters, and Right Leg Drive (RLD) circuitry onto a single module to optimize Common Mode Rejection Ratio (CMRR) and reduce PCB footprint. Experimental evaluations were conducted across varying input signal periods (4.00 ms to 80.0 ms) and external resistor configurations using a digital storage oscilloscope. Results demonstrate that lower input frequencies yield significantly higher amplification, achieving peak-to-peak output voltages (Vpp) of 14.0 V and 15.2 V with total gains of 14.000x and 15.200x at input periods of 40.0 ms (25 Hz) and 80.0 ms (12.5 Hz), respectively. This frequency-dependent gain scaling matches the dominant low-frequency spectrum of physiological ECG signals (0.05 Hz to 150 Hz). However, certain high-resistance setups (e.g., 986 kΩ) induced signal saturation, underscoring the necessity of precise component selection. Overall, the prototype provides a reliable, adaptable, and low-cost solution for wearable cardiac monitoring systems.