Low-Power Two-Stage Miller-Compensated Operational Amplifier for On-chip Biomedical Applications

Emerging wearable devices for biomedical applications and Lab on a Chip (LoC) are rapidly expanding in the electronic market. These devices integrate CMOS-based biosensors for monitoring, measuring and manipulating biochemical reactions in the same system. Biomedical signals and biosensor outputs typically operate at frequencies below 1 kHz and have amplitudes in the $\mu \mathrm{V}$ range. These systems are crucial for low-frequency signal processing in biomedical, biophysical, and biochemical applications. To meet the stringent power constraints of battery-operated wearable devices, the design of analog components like operational amplifiers (OpAmps) must prioritize low power consumption, compact size, and high performance. This paper presents a subthreshold-biased OpAmp design optimized for low-power operation in TSMC $0.18 \mu \mathrm{~m}$ technology. Leveraging subthreshold biasing and Miller compensation techniques, the OpAmp achieves a DC gain of 63 dB with a power consumption of 49 nW and a supply voltage of 1 V. Post-layout simulations confirm stable operation with a phase margin of 64.4° and a gain-bandwidth product of 12.6 kHz. These results demonstrate the OpAmp’s suitability for accurate amplification and processing of low-amplitude and low-frequency biomedical signals.