Ambient and component temperature has a decisive impact on the performance and
lifetime of electronic equipment. There is hardly any system without at least one sensor
to acquire temperature values and feed them back to the digital processing units or
analog control circuits. This application note provides an overview of three accurate and
cost-optimized solutions for a wide range of temperature sensing applications.
One of the simplest and lowest cost solutions features a forward biased diode (Fig. 1).
The voltage drop between anode and cathode is a function of both current and temperature.
Due to the silicon’s physical characteristics, a diode’s forward voltage will
vary with temperature by a ratio of ca -1.6 m V/K (K designates the difference of two
temperatures in °C). Driving the diode with a constant current will eliminate its dependency
of current and turn it into a temperature sensor with an almost linear output
characteristic. As self-heating of the diode will bias the measurement, it is important to
keep the forward current at a minimum. A few mA will be enough to enable temperature
measurement.
Almost any type of rectifier diode will do the job. Diotec offers a wide range of solutions in
all commonly used packages:
