A linear temperature-to-frequency converter using a thermistor

A novel technique for output frequency linearization of a thermistor-astable multivibrator is presented. An analytical expression for the linearity condition is obtained and demonstrated experimentally. The astable multivibrator incorporating this technique is shown to offer an approximately linear temperature-to-frequency conversion in the range 0 to 86°C with a sensitivity of 21 Hz/°C. The experimental circuit exhibits excellent thermal stability for ambient temperature variations. The technique can also be used successfully in the lower temperature range −50 to 0°C.