This paper presents the design of an integrated temperature sensor. The sensor was manufactured using the 3 µm CMOS technology. The proportional to absolute temperature sensor output signal was produced by two MOS transistors with biasing and buffering circuits. The sensor output voltage was linearly proportional to the absolute temperature in a wide range of temperature values. The measurement results coincide very well with the results of the process corner analysis. Certain non-linearities occurring at high temperature values are investigated in this paper in more detail. Additionally, the influence of neighboring circuits present in the manufactured integrated circuit on the sensor temperature response is studied.