A Nanopower Biopotential Lowpass Filter Using Sub threshold Current-Reuse Biquads With Bulk Effect Self-Neutralization
Abstract : A nanopower CMOS 4 th -order lowpass filter suitable for biomedical applications is presented. The filter is formed by cascading two types of subthreshold current-reuse biquadratic cell. Each proposed cell is capable of neutralizing the bulk effect that induces the passband attenuation. The nearly 0 dB passband gain can thus be maintained while the entire filter circuit remains compact and power-efficient. Designed for electrocardiogram detection as an example of application, the filter prototype has been fabricated in a 0.35 µm CMOS process occupying 269 µm × 383 µm chip area. Measurements verify that the filter can operate from a 1.5 V single supply and consumes 5.25 nW while providing a cutoff frequency of 100 Hz and input-referred noise of 39.38 µVrms. The intermodulation-free dynamic range of 51.48 dB is obtained from a two-tone test of 50 and 60 Hz input frequencies. Compared with state-of-the-art nanopower lowpass filters using the most relevant and reasonable figure of merit, the proposed filter ranks the best.
? The existence of a transmission window, flanking a polariton minimum, extends well into the stable regime.
? In this regime, the system demonstrates a stark duality in signal transport, marked by the possibility of achieving both transparency and opacity, for the same set of system parameters.
? The greater signal sensitivity and control incorporated by the an harmonicity could be harnessed for the design of photonic devices with optical switching properties.
? However, there exists no single allen compassing quantum system capable of holding up to all the requirements and vital performance metrics of a modern day signal-processing network.
? This paper tackles the aforementioned problem by introducing two current-reuse CMOS biquads so that their problems of bulk effect can be neutralized.
? We tried to mitigate the mismatch problem by combining common centroid and inter-digitation layout techniques to all current mirror circuits.
? The impact of transistor mismatch could be further lowered, applying larger transistor channel sizes, at the cost of silicon area of the filter.
? Switched capacitor (SC) filters are not suitable for lowfrequency applications as they suffer from clock feed-through and leakage problems in advanced processes.
• The CMOS structure of the proposed filter utilize the bulkdriven technique and operates in subthreshold region to achieve extremely low-voltage supply (0.3V) and nanopower consumption (0.676 nW) for cut-off frequency of 100 Hz.
• In this paper we propose a new solution for an ULV ECG filter based on the BD approach.
• The filter is a cascade connection of two newly-proposed second-order (biquad) filters, developed from a compact current re-use CMOS buffers.
• This idea has been next adopted to signal filtering purposes, in a similar way as described.
? The slope factors of pMOS (np) and nMOS (nn) are slightly different and this can also be another non-ideality affecting the filter performance apart from the bulk effect.
? This is in line with the fundamental trade-off in analog design that to achieve low noise performance for a certain fC, we need to sacrifice capacitive area and current consumption.
? This represents the standard form of a second-order transfer function with a unity passband gain that can be used for cascade design of a higher-order LPF.
? In this design, the bias currents are in the range of a few nanoamperes or below, and all transistors used are largely sized, the flicker noise can be neglected and the shot noise becomes dominant.
|