Embodiments presented herein describe a voltage mode log-domain low pass filter (LDLPF) tailored for health care applications such as ECG and EMG. The LDLPF operates in voltage mode, with input and output in voltage, allowing integration with voltage-based signal chains. The filter's bandwidth is dynamically programmable by varying bias currents, which are controlled by a variable control voltage applied across a set of transistors. The system enables a flexible measurement signal conditioning circuit that includes multiple channels and programmable gain stages using operational transconductance amplifiers (OTAs). This design provides power efficiency, high signal integrity, and wide adaptability across patient-dependent signal variations.
Figure (1) Test plan of Log domain Low pass Filter (LDLPF)
Traditional signal conditioning circuits for biomedical signals (ECG, EMG) often use current-mode filters that limit their programmability and integration with voltage-based analog front ends. These systems struggle to meet the wide variability in patient signal amplitude and frequency while maintaining low noise, power, and compact design constraints.
- Voltage-Mode Architecture: The LDLPF operates entirely in voltage mode, with voltage input and output, ensuring seamless compatibility with conventional analog front-end circuits commonly used in biomedical instrumentation, unlike traditional current-mode filters.
- Tunable Bandwidth Control: The filter’s bandwidth is continuously programmable by adjusting a control voltage, which regulates bias currents through internal transistors. This allows precise tuning of the -3 dB cut-off frequency from 150 Hz to 11 kHz, adapting effectively to the diverse signal ranges found in ECG and EMG applications.
- Log-Domain Low-Pass Filtering (LDLPF): Using a log-domain gm-C structure with exponential current-voltage behavior, the filter achieves low-power consumption and compact design while providing accurate analog signal processing for physiological data.
- Programmable Gain Using OTAs: The system incorporates OTAs configured in a feedback-based non-inverting amplifier topology, offering selectable gain levels of 2 dB, 10 dB, and 20 dB, which helps maintain signal quality regardless of varying patient-specific signal amplitudes.
- Multi-channel Configurability: The design supports multiple independent signal channels, each with its own instrumentation amplifier and filtering stages, enabling parallel processing of biosignals in multi-lead ECG or EMG systems with consistent performance.
The prototype LDLPF circuit was designed to process biomedical signals such as ECG and EMG. It consists of a two-stage architecture: an ultra-low-noise instrumentation amplifier providing 34 dB gain, followed by an OTA-driven filter stage with programmable bandwidth. The filter is built using transistors configured in a log-domain gm-C topology, with bias current controlled by a voltage (Vcntr) ranging from 850 mV to 1.2 V. This allows the cut-off frequency to be programmed from 150 Hz to 11 kHz. The gain setting is managed by a feedback network involving off-chip switches, supporting discrete steps (2, 10, and 20 dB). Simulations validate the programmable nature of the design, suitable for diverse physiological inputs.
A fully designed and functionally described voltage-mode LDLPF has been developed and simulated for healthcare applications. The circuit offers programmable bandwidth from 150 Hz to 11 kHz by adjusting a control voltage, and is optimized for use in ECG and EMG signal conditioning.
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This innovation can significantly improve the reliability and flexibility of low-power health monitoring systems. It supports wearable or portable biomedical devices that need precise, patient-specific signal conditioning. This helps in early diagnosis, long-term monitoring, and personalized healthcare, especially in resource-constrained or remote settings.
- Electrocardiography (ECG) and Electromyography (EMG) equipment
- Wearable health monitoring devices
- Remote diagnostics and telemedicine
- Biomedical signal acquisition ICs
- IoT-based health sensing platforms
- Medical electronics R&D
Geography of IP
Type of IP
4557/MUM/2015
398460