Describes a low-noise, low-power and low-voltage amplifier dedicated to very low amplitude signal acquisition from implantable electronic devices. Low noise and low DC offset are realized by means of chopper stabilization (CHS) technique. In addition, due to adding a rail to rail input stage, low power supply (1.8V) and wide common mode input range (0-1.8V) are achieved. It features a gain of 51dB and a bandwidth of 4.5 kHz. The equivalent input noise is about 56nv//spl radic/(Hz).