Circuit and device for small photo currents and detection of small photo currents

A bridge circuit arrangement comprising:

• a first photodevice configured on a first arm of the bridge circuit arrangement;
• a second photodevice configured on a second arm of the bridge circuit arrangement;
• a first resistor configured on a third arm of the bridge circuit arrangement, the first resistor being a variable resistor;
• and
• a second resistor configured on a fourth arm of the bridge circuit arrangement, the second resistor being a constant resistor,
• the first and second photodevices each providing a current in response to illumination, wherein the flow in opposing directions, and
• wherein the first resistor has a coefficient of resistance corresponding to wherein there is no net current flowing between the first photo device and the second photodevice.

A method of configuring a bridge circuit arrangement, the method comprising:

• providing a first photodevice on a first arm of the bridge circuit arrangement;
• providing a second photodevice on a second arm of the bridge circuit arrangement;
• providing a first resistor on a third arm of the bridge circuit arrangement, the first resistor being a variable resistor;
• providing a second resistor on a fourth arm of the bridge circuit arrangement, the second resistor being a constant resistor;
• directing the first and second photodevice in order to provide current flow in opposing directions;
• configuring the first photodevice on the first arm with a third resistor having an equivalent resistance to the first photodevice;
• configuring the second photodevice on the first arm with a fourth resistor having an equivalent resistance to the first photodevice;
• and
• providing no external power to the bridge circuit arrangement.