A VCO-based ADC with Relaxation Oscillator for Biomedical Applications

Abstract

This paper describes a voltage controlled oscillator (VCO)-based ADC for biomedical applications which employs a relaxation oscillator for voltage-to-frequency conversion. The proposed circuit uses a redundant pair of capacitors to mitigate the conversion error resulting from the time required for resetting the capacitor. A switch matrix with feedback helps sustain oscillations. Further, the VCO frequency approaches zero as the input voltage approaches zero unlike a converter with ring oscillator, thereby reducing power consumption. Post-layout simulation of the proposed ADC designed with a 28 nm FDSOI CMOS technology shows an ENOB of 8 and power consumption of 12 W from a 0.7 V supply.

0.5 V Universal Filter and Quadrature Oscillator Based on Multiple-Input DDTA

“…The analog filters are used to select the required frequency range (in case of the bandpass filters) and to eliminate the out-of-band noise (in case of the low-pass filters). There are many low-voltage and low-power analog filters [21], [22], [23], [24], [25], [26], [27], [28], as well as signal generators [29], [30], [31], [32] available in the literature. The universal filters and oscillators based on low-voltage and low-power DDTAs have been proposed in [21] and [22].…”