ContinuousaCMOS technology scaling increases both number of MOS devicesaand power density in a VLSIacircuit, which results in multiple hotspotsaduring its operation. Hence, on-chip thermal monitoring of these multiple hotpotsabecomes necessary due to circuit safety purposes and management as well. However, temperature sensors foraon-chip thermal monitoring must fulfill three other major requirements: small area, low poweraconsumption, and high supply voltage scalability [1], [2]. To reduce the occupied area and power consumption, multiple small sensing elements are distributed at the hot spots. The demand foraaccurate relative temperature sensing may be higher than that for the absolute temperature sensing to balance loads of different processor cores [3]. A large variety of temperature sensorsahave been developed to match wide varying technical and economic requirementsaof different applications. Namely, Bipolar based, MOSFET based, On-chip Resistors based, and Thermal diffusivity based. Nowadays, finding its application in many different fields, the on-chip thermal sensors offer clear room for improvements and have been chosen topic of this thesis work.In this work, a higher resolution and linear on-chipatemperature sensor was designed in the cadence virtuoso platform with Spectre simulator using SCL_PDK library in 180nm CMOS technology, which utilizes 1.8V supply voltage. The design is doneaon the concept of a thresholdvoltage-based temperature sensor, where the circuit provides temperature information in the form of output voltage, which is linear over a selected temperaturearange. Self-biased VDD-insensitive bias generator circuits that express the threshold voltage at the output have been used to build threshold voltage based (VTH-based) temperature sensors [4], [5]. An analysis of the circuit has been done using a square-law model for MOS transistors with zero output conductance, and it shows that this circuitry is power supply independent (given that all the MOS transistors are in saturation) with the output voltage linearly dependent on the threshold voltage. The circuit in the 180 nm technology operates in the military temperature range [-55o C to 125o C], offers a thermal sensitivity of -1.8 mV/ o C, consumes only 53.1 𝜇𝑊 of power, and requires an extremely small area of 87.98 𝜇𝑚2. It shows a maximum INL error of +2 o C across the temperature range [40 o C, 80 o C].