Abstract
This paper presents a high-speed ring oscillator (RO) with amorphous Indium-Gallium-Zinc-Oxide Thin-film transistors (a-IGZO TFTs). The proposed RO reduces the delay of a single stage inverter using intermediate signals generated within the RO, hence, improving the speed. To validate the proposed idea, two conventional ROs (with diode-load load inverter and bootstrapped pseudo-CMOS inverter) and the proposed RO were fabricated at a temperature ≤ 180°C. Measured results of the proposed RO have shown a frequency and power-delay-product (PDP) of 173.2 kHz and 0.7 nJ at a supply voltage of 6V. Further, it shows approximately 155% (44%) increase in frequency and 14% (24.5%) decrease in PDP compared to diode-load inverter (bootstrapped pseudo-CMOS inverter) based ROs. Therefore, the proposed RO finds applications in low-voltage and high speed designs for timing signal generation.
Highlights
Amorphous Indium-Gallium-Zinc-oxide thin-film transistor (a-IGZO TFT) technology has various advantages compared to other TFT technologies [1]–[3], which extend its applications into various domains as RFID tags, high-resolution display drivers, biosensor readout circuits or radiation sensing system [4]–[9]
The voltage transfer characteristics (VTC) of the inverters employed in the Ring Oscillators (RO) were measured using the probe station
The characteristic had been obtained by linearly sweeping the input voltage of the inverter (VIN) from -5 V to 6 V in a step size of 0.1 V
Summary
Amorphous Indium-Gallium-Zinc-oxide thin-film transistor (a-IGZO TFT) technology has various advantages compared to other TFT (organic and a-Si:H) technologies [1]–[3], which extend its applications into various domains as RFID tags, high-resolution display drivers, biosensor readout circuits or radiation sensing system [4]–[9]. The low-cost solution would be to address the technology limitation for better performance through circuit design techniques without changing the device structure, materials or fabrication processing steps, and additional supply voltage source. Fulfilling these premises, this work proposes a high speed RO, where high frequency of oscillation is obtained at low VDD by reducing the delay of an inverter stage using intermediate signals generated within RO. It can be an optimal choice for on-chip clock generator even in low-voltage applications.
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