Indirect programming of floating-gate transistors

Floating-gate (FG) transistors are useful for precisely programming a large array of current sources. Present FG programming techniques require disconnection of the transistor from the rest of its circuit while it is being programmed. We present a new method of programming FG transistors that, does not require this disconnection. In this indirect programming method, two transistors share a FG allowing one to exist directly in a circuit while the other is reserved for programming. Since the transistor does not need to be disconnected from the circuit to program it, the switch count is reduced, resulting in fewer parasitics and better overall performance. Additionally, the use of these indirectly programmed FG transistors allows a circuit to be tuned such that the effects of device mismatch are negated. Finally, the concept of run-time programming is introduced which allows a circuit to be recalibrated while it is still operating within its system.