Abstract
Abstract. This paper presents an electrical, fully integrated, high quality (Q) factor GmC bandpass filter (BPF) stage for a wireless 27 MHz direct conversion receiver for a bendable sensor system-in-foil (Briem et al., 2016). The core of the BPF with a Q factor of more than 200 is an operational transconductance amplifier (OTA) with a high linearity at an input range of up to 300 mVpp, diff. The OTA's signal-to-noise-and-distortion-ratio (SNDR) of more than 80 dB in the mentioned range is achieved by stabilizing its transconductance Gm with a respective feedback loop and a source degeneration resistors RDG. The filter stage can be tuned and is tolerant to global and local process variations due to offset and common-mode feedback (CMFB) control circuits. The results are determined by periodic steady state (PSS) simulations at more than 200 global and local process variation parameter and temperature points and corner simulations. It is expected, that the parasitic elements of the layout have no significant influence on the filter behaviour. The current consumption of the whole filter stage is less than 600 µA.
Highlights
1.1 MotivationFor the realization of a mechanical flexible sensor systemin-foil all rigid components, like crystal oscillators as frequency reference, have to be avoided
The bandpass filter (BPF) is realized by a GmC circuit, which only consists of operational transconductance amplifier (OTA) with the transconductance Gm and capacitors with the capacitance C, and can be well integrated in common CMOS technologies (Wangenheim, 2008; Schaumann et al, 1990)
With the basic GmC circuits, a GmC BPF stage can be realized with 4 OTAs and two capacitors
Summary
For the realization of a mechanical flexible sensor systemin-foil all rigid components, like crystal oscillators as frequency reference, have to be avoided. To keep the foil system simple and flexible, an integrated on-chip BPF is desired. As inductors for lower frequencies are quite large, and Q factors of on-chip inductors are very limited, they are replaced by active components. Since resistors use a large area on the chip and no clock reference is available, neither RC filters nor switched-capacitor circuits can be used. The BPF is realized by a GmC circuit, which only consists of OTAs with the transconductance Gm and capacitors with the capacitance C, and can be well integrated in common CMOS technologies (Wangenheim, 2008; Schaumann et al, 1990)
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