| IP개요 |
This circuit is biopotential signal acquisition analog front end (AFE) to measure biopotential signal, for example electromyogram (EMG), electrocardiogram (ECG) and electroencephalogram (EEG). Because this signal is electronic, the boipotential signal is obtained by using the electrode, dry or wet electrode. There is existed DC offset voltage, the offset voltage between the electrode and body skin. For example, the polarization of the Ag/AgCl wet electrode has DC offset voltage within the range of one to tens mV. Because of this DC offset voltage, the biopotential signal has distortion and then quality of the output signal is decreased. So, to reject the DC offset distortion, high input impedance is needed for AFE. Also, the biopotential signal has very small amplitude within the range from uV to mV on the frequency under hundreds Hz. Then, the basic cell is needed to decrease the flicker noise. To decrease the flicker noise, this circuit has chopper stabilization. The output signal of the amplifier with the chopper stabilization is increased by using programmable gain amplifier. The amplifier of the each stage is designed for the low power. The proposed circuit is low power biopotential acquisition analog front end with multiple feedback loops. For the fine acquisition of the biopotential signal, the input impedance boosting loop is used for high input impedance. And for low noise and distortion, capacitively coupled chopper-stabilized instrumentation amplifier (CCIA) unit is used and dual common mode feedback (CMFB) is designed by using the feedback loop of the main amplifier and resistive CMFB. Also, each CCIA unit has DC servo loop (DSL) and ripple reduction loop (RRL). These loops with various functions are needed for the low noise, low power and high performance. The chip is implemented using 0.18 um complementary metaloxide-semiconductor (CMOS) process. The power consumption is 3.3V supply voltage. The maximum operating frequency is 10MHz. |
