Programmable reference voltage source, particularly for analog memories

摘要

A programmable reference voltage source includes a nonvolatile memory cell, the floating-gate region of which stores electric charges determining a memorized threshold value. The drain terminal of the cell is biased at a constant voltage, and the source terminal is coupled to a constant-current source and to the inverting input of an operational amplifier having the noninverting input coupled to a reference voltage and the output coupled to the gate terminal of the cell. By defining the threshold of the cell as the gate voltage (measured with respect to ground) capable of causing the cell to be flown by the current set by the current source, the output voltage of the operational amplifier equals the threshold and may be used as a programmable reference in analog memories.