||In recent years, medical technology is the very hot research topics as people pursue healthy life style in modern world. Different kind of hereditary diseases have been discovered and related to DNA pattern. As a result, DNA detection is one kind of bio-signal detection which is important in medical technology. The bio-signal detection is normally current based rather than voltage based because it does not require time for charging. As the bio-signals may need to further process after detection, high performance current memory cells are required. In this thesis, a new current sample and hold cell for weak bio-medical application is proposed. This circuit introduces a method of constant charge injection on the sampling stage. Also, the memory transistor operates in weak-inversion for processing weak signal current in nano-ampere range such that effect due to distortion can be minimized. The designed current cell operates in weak current with power consumption of 0.7μW. The results are simulated with 0.35-μm technology through Cadence, and the proposed circuit has been successfully implemented in AMS 0.35μm CMOS technology. The simulation results and measurement results have been introduced, and show the current cell can process weak signal properly with sampling speed equal to 2kS/s with the best SNDR achieved equals to 59dB.