Hall-effect device driver with temperature-dependent sensitivity compensation

摘要

A Hall-effect device for detecting a magnetic flux intensity has a pair of input terminals connected respectively to a constant-voltage regulated power supply and an FET. The FET has a gate connected to the output terminal of an operational amplifier. One of the input terminals of the operational amplifier is connected to the junction between a variable resistor and a temperature-dependent variable resistor which jointly serve as a voltage divider. The temperature-dependent variable resistor has a temperature characteristic of resistance which is opposite to the temperature characteristic of sensitivity of the Hall-effect device. When the ambient temperature varies, the sensitivity of the Hall-effect device also varies, and so does the resistance of the temperature-dependent variable resistor. The divided voltage applied from the voltage divider to the operational amplifier drops, lowering the voltage applied to the gate of the FET. The internal resistance of the FET also decreases to lower a drive current flowing through the Hall-effect device for thereby compensating a temperature-dependent sensitivity change of the Hall-effect device. Therefore, the sensitivity of the Hall-effect device remains constant.