Harnessing the VO 2 Phase Transition for Automatic Gain Control in Transimpedance Amplifiers

Abstract

Transimpedance amplifiers (TIAs) convert input currents into output voltages in sensor electronics. Conventional TIAs utilize fixed‐gain resistors, which saturate under high input currents, resulting in undesirable recovery times. To overcome this, volatile resistive switching devices emerge as a promising alternative, offering intrinsic automatic gain control (AGC). Among these, vanadium dioxide (VO 2 ) devices stand out for their reversible insulator–metal transition (IMT), producing abrupt, energy‐efficient resistance changes near the transition temperature ( T C ≈ 67°C). In this work, switching devices were fabricated by sputtering a VO 2 thin film and patterning ∼200 nm electrode gaps. Before TIA integration, the switching dynamics were characterized under electrical pulse excitation. Slightly exceeding the temperature‐dependent IMT threshold voltage yields fast, reproducible switching. Pump–probe measurements show that operating well below T C suppresses short‐term memory effects linked to the stochastic first‐order transition. Leveraging this, a VO 2 ‐based TIA was developed, demonstrating variable gain and AGC functionality. Furthermore, applying a constant DC current bias during switching induced self‐sustained oscillations (∼1.5 pJ per oscillation) of up to ∼60 MHz, consistent with the VO 2 thermal timescale. Overall, these results provide a detailed understanding of VO 2 switching dynamics and demonstrate their potential for enabling compact, energy‐efficient AGC in high‐speed TIAs for advanced sensing.