1. A transformer for coupling to a material stack, the transformer comprising: a first winding operatively coupled to a first conductive contact layer of the material stack, the material stack having a variable resistive layer, a fixed resistive layer, and a second conductive contact layer, the variable resistive layer and the fixed resistive layer being positioned between the first and second conductive contact layers; and a second winding operatively coupled to the second conductive contact layer, the first and second windings having a differential configuration where, upon injection of an electron stream into the material stack, a vector sum of a third magnetic field is generated by the first and second windings and is applied to a third winding such that a current difference between the first and second windings is detected and presented as an output of the third winding; the first and second windings are arranged to present opposing magnetic fields relative to each other in response to current applied to the material stack by the electron stream, and in response to the magnetic fields generated by the first and second windings, the third winding is to generate a proportional output signal resulting from a difference in current distributions in the material stack due to the difference between a first resistive state and a second resistive state of the variable resistive layer resulting in a proportional response in the magnetic fields generated by the first and second windings based on the difference in current between the first and second conductive contact layers.