Archive for August, 2010

Sensing Bidirectional Current With a Single Supply Op-amp

The circuit is essential the same as an operational amplifier in a differential amplifier configuration. The important difference is, instead of connecting the non-inverting input to ground, it is connected to a buffered voltage which is equal to half of your ADC reference voltage.

Bidirectional Current Sensing Schematic

Bidirectional Current Sensing Schematic

In software, you retrieve an unsigned value from the ADC register, copy it to a signed integer value and subtract half of the top value. For example, for a 10-bit ADC:


If your ADC supports differential conversions, You can still use the above and save a pin; or you can direct VHALF into the inverting input and the op-amp output into the non-inverting input and convert with a signed result.