This paper presents two compact frequency-output temperature sensors based on a multivibrator current-to-frequency converter to improve sensor linearity over a wide temperature range featuring low-voltage low-power operation. Both sensors have been fabricated in a low-cost 0.18-μm CMOS technology with a single 1.2 V supply voltage. They show high linearity over a temperature range of -40°C to +120°C, achieving an inaccuracy of ±1°C, with sensitivities of 335 Hz/°C and 460 Hz/°C, a power consumption below 3 μW, and an area below 0.025 mm². These features make them a highly suitable solution in the case of portable applications.