Abstract
In this thesis, an automatic gain cotnrol amplifier for implantable microsystem of deep brain stimulation (DBS) is proposed. DBS is a prodecure that using neurostimulator to send electrical pulse to specific targets in brains. Pakinson disease is one of the indications of DBS. In order to measure the response from brain, an analog front-end is needed to capture the local field potential. High voltage spindle is one type signal of local field potential which founded in parkinson disease induced rat’s basal ganglia. In order to avoid the saturation caused by high voltage spindle, the binary switch control method is proposed. With the method, neural signal would be amplified to specific range until the front-end is set to the largest gain set. The system provides three gain sets, 53.7dB, 59.7dB and 65.7dB. The low pass corner is 1.57KHz, and the high pass corner ranges from 0.05Hz to 5Hz. The gain is control by a digital circuit which can operate from 5KHz to 50KHz. The total power consumption is 6.9uW with 5.4uV input referred noise. The thesis has four chapters. In chapter1, we would review the backgroud of the implant device. The consideration and design of the system would be introduced in chapter2. The chapter3 shows the implementation of the automatic gain control ampilifer, simulation and measurement result. The conculsion and future work would be shown in chapter4 Keywords –Closed-loop system, Low-noise amplifiers, Implantable micro system, Neural amplifier.