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This paper presents an amplitude-shift-keying (ASK) demodulator for RF identification tags, which can be embedded on panel displays. The ASK demodulator was implemented in 3-[micro]m low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) technology. Since the threshold voltages of LTPS TFTs are higher than CMOS transistors, the conventional demodulator implementation will degrade the demodulator sensitivity significantly. The novel full-wave demodulator circuit was proposed to resolve the issue of high threshold voltage and reduce the ripples of the demodulated envelope. Operated at 8 V, the demodulator consumes 1.6 mW of power. The input carrier frequency was tested up to 13.56 MHz, and the highest ASK modulated data rate is 100 kb/s. The circuit size of the LTPS TFT demodulator is 500 [micro]m x 450 [micro]m. Index Terms--Demodulator, low-temperature polycrystalline silicon (LTPS), RF identification (RFID), system on panel (SOP), transponder.

A phase-locked loop (PLL) with self-calibrated charge pumps (CPs) has been fabricated in a 3-[micro]m low-temperature polysilicon thin-film transistor (LTPS-TFT) technology. A voltage scaler and self-calibrated CPs are used to reduce the static phase error, reference spur, and jitter of an LTPS-TFT PLL. This PLL operates from 5.6 to 10.5 MHz at a supply of 8.4 V. Its area is 18.9 [mm.sup.2], and it consumes 7.81 mW at 10.5 MHz. The measured static phase error without and with calibration is 80 and 6.56 ns, respectively, at 10.5 MHz. The measured peak-to-peak jitter without and with calibration is 3.573 and 2.834 ns, respectively. The measured reference spur is -26.04 and -30.2 dBc without and with calibration, respectively. The measured maximal locked time is 1.75 ms. Index Terms--Calibration, charge pump (CP), low-temperature polysilicon thin-film transistor (LTPS-TFT), phase-locked loop (PLL).

Inverted thin-film transistors (TFT) with a self-aligned, lightly doped drain (LDD) structure are studied. The LDD structure, which was fabricated via a spacer process minus thesubsequent lithography, enables regulation of the channel electric field at thedrain junction for enhanced device operation. Experiments to quantify the device's current-voltage properties show a saturation current of around 11.25 micro-A at five V and a leakage current of around 0.03 pico-A per micrometer ofchannel width.