A sensing device comprises a charge pump, a MEMS sensor, a source follower and a PGA. The charge pump is configured to provide a pump voltage. The MEMS sensor is electrically connected to the charge pump and configured to generate an input voltage according to environment variations. The source follower is electrically connected to the MEMS sensor and configured to generate a followed reference voltage according to the pump voltage and to generate a followed input voltage according to the input voltage. The PGA has an input end of the PGA electrically connected to the source follower and is configured to generate two-ended differential output voltages outputted through a first output end and a second output end according to a difference between the followed reference voltage and the followed input voltage.