| dc.description.abstract | With the popularity of the mobile devices, more and more portable biomedical electronic products have been launched. In addition to providing immediately medical supervision for elders and people who need long-term care, these products can measure the heartbeat, blood pressure and muscle strength for people taking exercise. With the wireless transmission technology, these physiological signals detected by read-out circuit will be synchronized to mobile device for advanced analysis. Because the signals acquire from human body usually feature extreme low amplitude, the ability to completely amplify these signals in portable device without introducing noise or interference is main challenge faced by biomedical detection system. For this reason, this circuit is designed with the aim of low noise, low distortion and low power.
This thesis presents a design of analog front-end amplifier for bio-signal detection and is composed of low noise amplifier (LNA) and programmable gain amplifier (PGA). CCIA (capacitor-coupled instrumentation amplifier) architecture is applied to both parts for rejection DC offset of front-end electrode-tissue. Generally, bio-signal detection system for ECG and EEG require acquisition of low frequency signal at nearly 1 Hz. Although conventional CCIA architecture that uses pseudo-resistor as the feedback path can achieve such low cut-off pole, it will also introduce the distortion at low frequency. Instead, this thesis applies active integrator as feedback path to realize low cut-off pole. By doing so, we can reduce the demand for pseudo-resistor resistance, and then improve signal linearity at low frequency. The pseudo-resistor in the integrator applies voltage-controlled symmetric pseudo-resistor (VCSPR) to realize programmable bandwidth function. In programmable bandwidth range, this design can detect Electroencephalography (EEG), Electrocardiogram (ECG) and Electrooculography (EOG) signal.
This circuit is designed in TSMC 0.18 μm CMOS 1P6M process and the chip area is 0.834 mm2 (including ESD PAD). The power consumption is 4.1 μW for 1.2 V power supply voltage. The minimum low cut-off frequency is 1 Hz (programmable) and application bandwidth is 5 kHz. With PGA, the system gain can be 54 dB, 48 dB, 42 dB respectively. Finally, input-referred noise is 2.28μVrms and noise efficiency factor (NEF) is 2.29. | en_US |