This paper analyses how a single metal-oxide-semiconductor field-effect transistor (MOSFET) can be employed as a thermal sensor to measure on-chip dynamic thermal signals caused by a power-dissipating circuit under test (CUT). The measurement is subjected to two low-pass filters (LPF). The first LPF depends on the thermal properties of the heat-conduction medium (i.e. silicon) and the CUT-sensor distance, whereas the second depends on the electrical properties of the sensing circuit such as the bias current and the dimensions of the MOSFET sensor. This is evaluated along the paper through theoretical models, simulations, and experimental data resulting from a chip fabricated in 0.35 mu m CMOS technology. Finally, the proposed thermal sensor and the knowledge extracted from this paper are applied to estimate the linearity of a radio-frequency (RF) amplifier. (C) 2016 Elsevier B.V. All rights reserved.