Temperature Insensitive Low-Power Ring Oscillator Using only n-type Transistors

Abstract

A low-power five stage current starved ring oscillator which is robust against temperature variations is being presented in this work. The proposed work has been designed using only n-type transistors and therefore, can easily be adapted to amorphous oxide TFTs which have unstable p-type transistors. The ring oscillator uses temperature compensation biasing circuit, which contains a novel bootstrap op-amp. The biasing circuit generates constant bias voltage to make current starved ring oscillator insensitive to temperature variations. The proposed circuit simulations were done in Cadence Virtuoso on standard 180 nm CMOS technology with a supply voltage of 1.8 V. This circuit has shown a frequency of oscillation around 235.8 MHz and a power delay product of 0.139 pJ. The phase noise of designed ring oscillator is $-98.532$ dBc/Hz. It shows $3.73\%$ variations in frequency over a temperature range from −40$\,^{\circ }$C to 125$\,^{\circ }$C. Since oxide TFT’s are also n-type FET’s (Field Effect Transistors), the proposed design can be directly adapted to this emerging post-silicon technology, which finds potential applications in smart packaging, bio-medical and wearable systems [1].

Supported by IIIT Delhi.