An autozeroing floating-gate amplifier with gain adaptation

Recently, we have characterized and modeled floating-gate circuits that adapt their floating-gate charge based upon statistics of the incoming signal. In this paper, we show signal-dependent adaptation in three floating-gate circuits. First, we show classic autozeroing floating-gate amplifier (AFGA) measurements of output voltage adaptation, as well as AFGA measurements of offset adaptation for large output amplitudes. Second, we measure and characterize current adaptation of a transconductance element, where the current increases for increasing signal level. Third, we measure and characterize the amplitude and offset adaptation in a floating-gate circuit built from the first two circuits; amplitude adaptation only occurs over a finite range of input parameters and timescales. Floating-gate circuits using continuous tunneling and injection naturally adapt the floating-gate charge in response to various applied input signals. Our previous investigations have shown basic adapting circuits, like the autozeroing floating-gate amplifier (AFGA), that adapt away a single feature of an incoming signal. Recently, we have: characterized and modeled floating-gate circuits that adapt their floating-gate charge based upon statistics of the incoming signal. This result is the first indication that floating-gate devices with continuous tunneling and hot-electron injection currents are capable of large-scale adaptation. This paper continues this work by showing signal-based adaptation in three floating-gate circuits. In the third circuit, we show amplitude adaptation over a finite range of input parameters and timescales