Low-noise variable-temperature preamplifier for piezoelectric tuning fork force sensors

The development of a low-noise variable-temperature preamplifier for self-sensing piezoelectric tuning fork force sensors is presented. The preamplifier utilizes a pair of commercially available GaAs field effect transistors to achieve high impedance and low noise over a wide range of temperatures. Using a standard 32 kHz quartz tuning fork, the base noise level achieved is 20 dB below the thermal noise resonance at room temperature and at 4.2 K. The circuit diagram, biasing points, and noise specifications are presented, and the application for variable temperature scanning probe microscopy is discussed. (C) 2002 American Institute of Physics.