High-Bandwidth Feedback Control of Micromachined Tunneling Sensors

Displacement transducers based on quantum tunneling have been demonstrated for use in accelerometers, IR sensors, and other devices. An important characteristic of the tunneling transducer is that the tunneling current only occurs when the electrodes are separated by a gap of order 10 Å. Because of the requirement for a 10 Å gap between tunneling electrodes, a feedback control system is necessary to balance the signal forces to a very high degree of accuracy over the entire expected signal bandwidth. In this paper, we study several tunneling sensor control systems, with the goal of improving the control bandwidth. With our model analysis, a control bandwidth of 50 kHz is predicted, which is in excellent agreement with the measured bandwidth for these devices.