Memory circuits and systems are provided. One memory circuit includes an active memory device, an inactive memory device, and a sense amplifier coupled between the active memory device and the inactive memory device. A reference current is coupled between the inactive memory device and the sense amplifier. The active memory device and the inactive memory device are the same type of memory device and the inactive memory device is a reference device with respect to the active memory device's current. A memory system includes a plurality of the above memory circuit coupled to one another. Methods for sensing current in a memory circuit are also provided. One method includes supplying power to a first memory device and comparing the amount of current in the first memory device and a reference current coupled to a second memory device that is the same type of memory device as the first memory device.