In examples of a chopper operational amplifier, a current control circuit comprises a pair of voltage sources, each of which may be varied to generate a voltage signal of a particular value, and multiple inverters, each of which is configured to receive either a clock signal or its complement signal and one of the voltage signals. Based on these inputs, each inverter generates a control signal that is delivered to a corresponding switch in the input stage of the chopper operational amplifier to control the gate voltage of that switch. Based on the difference between the values of the voltage signals, the current control circuit operates to reduce the amplitudes of base currents induced by charge injection at the input terminals of the chopper operational amplifier.

Described herein is a front-end for a neural recording system that boosts input impedance of the front-end circuit. The front-end includes an amplifier and two choppers. A first input terminal of the first chopper may be coupled to a first output terminal from one or more signal sensors. A first input terminal of the second chopper may be coupled to a second output terminal from the signal sensors. A second input terminal of the first chopper may be coupled to a first output terminal of a feedback subsystem. A second input terminal of the second chopper may be coupled to a second output terminal of the feedback subsystem. The output terminals of each chopper may each be coupled to a different capacitor such that after switching, the voltage of each capacitor remains substantially the same, improving the input impedance of the circuit.

A Galvanically Isolated Amplifier (GIA) includes an isolation barrier to galvanically isolate high voltage circuitry from low voltage circuitry. The high voltage circuitry has at least two voltage supply rails, with the voltage supply rail closest to ground potential at a first potential relative to the ground potential. The low voltage circuitry has at least two voltage supply rails, with the voltage supply rail closest to the ground potential at a second potential, the second potential being smaller than the first potential. A Radio Frequency (RF) carrier is digitally Phase Shift Keying (PSK) modulated for transmission across the isolation barrier. The unmodulated RF carrier could also be transmitted across the isolation barrier. PSK modulation could be applied to the RF carrier based on a test waveform to generate a PSK-modulated test signal for transmission while a voltage transient is applied between the high voltage circuitry and the low voltage circuitry.

A chopper-stabilized amplifier that includes an analog driven level shifter is disclosed. The analog driven level shifter changes the levels of a pair of complementary clock signals according to a level associated with an input signal to the chopper-stabilized amplifier. The level shifted complementary clock signals are used to control switching devices used for chopping input signals of various voltages. The chopper-stabilized amplifier also includes symmetrical passive RC notch filters having two cut-off frequencies to reduce ripple noise from the chopping.

A signal error calibrating method is disclosed herein and includes following steps: filtering an error voltage in a sensor by a low pass filter in a calibration mode; converting the offset voltage to be a digital offset signal by an analog digital signal converter; converting the digital offset signal to be an offset calibrating signal by a digital analog signal converter; transmitting the offset calibrating signal to an input end of the sensor so as to offset an error voltage at the input end of the sensor. After calibrating the error voltage, the analog digital converter in the error calibrating circuit can be used for the need of signal output and the low pass filter is turned off at the same time.

A chopper amplifying circuit employing a negative impedance compensation technique, including a differential input end, a first-level chopper switch, a first-level amplifying circuit, a second-level chopper switch, a second-level amplifying circuit, a negative impedance converting circuit, a negative feedback unit, an input capacitor, and a differential output end, is provided. The differential input end is connected to the first-level chopper switch. An output terminal of the first-level chopper switch is connected to the first-level amplifying circuit through the input capacitor. The first-level amplifying circuit is connected to the second-level chopper switch, which is connected to the second-level amplifying circuit. The second-level amplifying circuit is connected to the differential output end, and is also connected to a feedback input end of the first-level amplifying circuit through the negative feedback unit. The negative impedance converting circuit is parallel-connected to a signal input end of the first-level amplifying circuit.

A chopper-stabilized amplifier that includes an analog driven level shifter is disclosed. The analog driven level shifter changes the levels of a pair of complementary clock signals according to a level associated with an input signal to the chopper-stabilized amplifier. The level shifted complementary clock signals are used to control switching devices used for chopping input signals of various voltages. The chopper-stabilized amplifier also includes symmetrical passive RC notch filters having two cut-off frequencies to reduce ripple noise from the chopping.

In a general aspect, a current sense amplifier circuit (CSA) can include a null amplifier path and a main amplifier path that are both configured to receive a differential input voltage. The null amplifier path can output a first differential output voltage based on the differential input voltage. The main amplifier path can also be configured to receive the first differential output voltage and output a second differential output voltage based on the differential input voltage and the first differential output voltage. The null and main amplifier paths can each include a differential amplifier having first and second input stages that are each configured to receive the differential input voltage. The first input stage and the second input stage of the main amplifier path can and be powered by a respective (first and second) floating voltage supply rails that are referenced to a floating ground rail.

A digital isolator device which includes a first input buffer configured to receive a first differential signal from a transmitter and to provide a second differential signal, the first differential signal being characterized by a first magnitude, the second differential signal being characterized by a second magnitude, the first magnitude being greater than the second magnitude. The device also includes a second input buffer configured to receive a third differential signal from the transmitter and to provide a fourth differential signal, the second input buffer being coupled to the second ground terminal. The device also includes a common-mode circuit coupled to the second differential signal and the fourth differential signal, the common-mode circuit being configured to reduce a common-mode transient voltage, the common-mode transient voltage being associated with a voltage differential between the first ground terminal and the second ground terminal.

A six phase capacitively coupled chopper amplifier. Two phases provide a zeroing phase to zero the feedback capacitors and set the input common mode value. Two phases provide a passive transfer of an input charge from the input capacitors to the zeroed feedback capacitors. The final two phases are chopping and amplification phases. The zeroing phases address the input common mode without the need for biasing resistors. The passive transfer phases resolve the glitching that occurs if the feedback capacitors have to be recharged on each cycle of the chopping clock. Resolving the glitching and the charge time allows the frequency of the amplifier to increase.