Non-contact capacitive electrodes are suitable for wearable devices to acquire electrophysiological signals in an unobtrusive and long-term way. However, due to its poorly-defined and low electrode capacitance, its front-end amplifier requires a large biasing resistance to maintain a sub-Hz high-pass frequency and low circuit noise. This paper compares two amplifier structures, i.e., a voltage amplifier and a charge amplifier, each with three biasing strategies, i.e., pseudo resistors, switched resistors and reset switches. These, in total six, amplifier designs were fabricated in a standard 180nm CMOS technology and compared in terms of their input impedance, transfer function and input-referred noise.