An Action Potential Detector Based on a High-Order Nonlinear Energy Operator

This paper presents an action potential detector (APD) based on a high-order non-linear energy operator (HONEO). The APD consists of a HONEO, a positive threshold generator, a negative threshold generator, and an XOR. The APD is capable of detecting the half-width of an action potential since it can determine both the positive peak and the negative peak of the action potential by means of the HONEO and two threshold generators. In addition, the signal-to-noise ratio (SNR) of the APD can also be improved due to the two adaptive threshold generators. The circuit is designed in a standard 0.18 μm CMOS process with a 1.8 V supply voltage. Pre-layout simulations are performed under typical conditions (TT process corner, 1.8 V supply, 27 ∘C). The results show that the output amplitudes of the HONEO remain almost constant (±100 mV) when the amplitude of the source signal varies from −10 mV to 30 mV at 1 kHz. Across temperature variations from −20∘C to 80 ∘C, the output amplitude remains within ±12% of the nominal value, demonstrating acceptable stability for the target implantable application. Compared to the conventional NEO, the APD achieves 14–20dB SNR improvement, a detection accuracy of 97%. The power consumption of the APD is approximately 62μW.