Thesis
A low noise low power dc-coupled sensor amplifier with offset cancellation
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/100226
Abstract
Modern research on studying animal behavior has a need for a variety of systems to record and analyze neural activities. This thesis involves the design of a DC-coupled low noise, low power sensor amplifier IC with DC offset cancellation. This chip consists of 16 independent channels which will be connected to multiple electrodes or an electrode array probing parts of the brain of the animal under study. Our application is mainly towards monitoring the neurological signals from mice without use of tether. This requires a wireless telemetry system with low mass and size. Each channel has amplification with programmable gain ranging from 20 to 2000 along with a filter. The power required per channel is about 1mW with a power supply of +/- 1 V. The bandwidth of each channel is 7kHz and has an input referred noise of about 0.495uV. A DC offset of up to +/- . 3 V can be canceled independently on each of the channels by adjusting the bulk voltages of the first stage amplifier. The amplification is obtained across two stages, the first stage with a programmable gain from 10 to 50 and the second stage with a gain of 2, 16 or 40. These stages are followed by buffers which deliver the differential signals to the A/D converter. An 8-bit resistor string DAC is used to control the bulk voltages of the input pair on the first stage amplifier to cancel the DC offset voltage. The DAC requires a bandgap reference of 1.5 V which is stable across temperature variations. The bandgap needs a higher voltage for its operation that is supplied by a charge pump PLL. The charge pump delivers a voltage of 3V which is sufficient to drive the bandgap. The chip was designed in the Jazz 0.18u CMOS process. Further improvement of the circuit to increase the offset cancellation to +/- 0.8 V would be helpful in some applications. One approach to accomplish this is to use voltages of 0, 0.5 and -0.5 in the feedback loop of the first stage amplifier.
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Details
- Title
- A low noise low power dc-coupled sensor amplifier with offset cancellation
- Creators
- Hari Krishnamurthy
- Contributors
- George S. La Rue (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Electrical Engineering and Computer Science, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525157501842
- Language
- English
- Resource Type
- Thesis