Note: Wide band amplifier for quartz tuning fork sensors with digitally controlled stray capacitance compensation

We presented a preamplifier design for quartz tuning fork (QTF) sensors in which the stray capacitance is digitally compensated. In this design, the manually controlled variable capacitor is replaced by a pair of varicap diodes, whose capacitance could be accurately tuned by a bias voltage. A tuning circuit including a single side low power operational amplifier, a digital-to-analog converter, and a microprocessor is also described, and the tuning process can be conveniently carried out on a personal computer. For the design, the noise level was investigated experimentally.