A method for a fast settling ripple reduction loop for high speed precision chopper amplifiers includes amplifying an input signal with a signal path to generate a first output, the signal path comprising chopping the input signal to generate a first chopper output, amplifying the first chopper output with an amplifier to generate an amplifier output and chopping the amplified output to generate a second chopper output. An output ripple of the first output is reduced with a Ripple Reduction Loop comprising chopping the second chopper output to generate a third chopper output, filtering the third chopper output with a filter to generate a Direct Current (DC) offset correction, and combining the DC offset correction with the amplifier output, wherein the third chopper output is driven to the output voltage of the filter and the RRL is disconnected from the low frequency signal path in response to a non-linear event.

A method for a fast settling ripple reduction loop for high speed precision chopper amplifiers includes amplifying an input signal with a signal path to generate a first output, the signal path comprising chopping the input signal to generate a first chopper output, amplifying the first chopper output with an amplifier to generate an amplifier output and chopping the amplified output to generate a second chopper output. An output ripple of the first output is reduced with a Ripple Reduction Loop comprising chopping the second chopper output to generate a third chopper output, filtering the third chopper output with a filter to generate a Direct Current (DC) offset correction, and combining the DC offset correction with the amplifier output, wherein the third chopper output is driven to the output voltage of the filter and the RRL is disconnected from the low frequency signal path in response to a non-linear event.

An amplifier including a P-channel transistor having current terminals coupled between a first node and a second node and having a control terminal coupled to a third node receiving an input voltage, an N-channel transistor having current terminals coupled between a fourth node developing an output voltage and a supply voltage reference and having a control terminal coupled to the second node, a first resistor coupled between the first node and a supply voltage, a second resistor coupled between the first and fourth nodes, and a current sink sinking current from the second node to the supply reference node. The amplifier may be converted to differential form for amplifying a differential input voltage. Current devices may be adjusted for common mode, and may be moved or added to improve headroom or to improve power supply rejection. Chopper circuits may be added to reduce 1/f noise.

Disclosed are a digital audio power amplifier and a power amplifier loop. The power amplifier loop comprises an operational amplifier U1, a capacitor C1, a power amplifier output stage, a resistor R1, a resistor R2 and a noise control unit, wherein an inverting input end of the operational amplifier U1 is respectively connected to one end of the capacitor C1, one end of the noise control unit and an output end of a preceding DAC current source; an output end of the operational amplifier U1 is respectively connected to a control end of the power amplifier output stage and the other end of the capacitor C1; an output end of the power amplifier output stage is successively grounded by means of the resistors R1, R2; the other end of the noise control unit is connected to a connection point between the resistors R1, R2; the resistance values of the resistors R1, R2 are set to satisfy R1/R2=(N−2)/2, where N>2; the reference voltage of the operational amplifier U1 is equal to PVDD/N, with PVDD being a power supply voltage of the power amplifier output stage; and the noise control unit is a resistor module. The present application ensures the normal operation of the digital audio power amplifier.

Disclosed are a digital audio power amplifier and a power amplifier loop. The power amplifier loop comprises an operational amplifier U1, a capacitor C1, a power amplifier output stage, a resistor R1, a resistor R2 and a noise control unit, wherein an inverting input end of the operational amplifier U1 is respectively connected to one end of the capacitor C1, one end of the noise control unit and an output end of a preceding DAC current source; an output end of the operational amplifier U1 is respectively connected to a control end of the power amplifier output stage and the other end of the capacitor C1; an output end of the power amplifier output stage is successively grounded by means of the resistors R1, R2; the other end of the noise control unit is connected to a connection point between the resistors R1, R2; the resistance values of the resistors R1, R2 are set to satisfy R1/R2=(N−2)/2, where N>2; the reference voltage of the operational amplifier U1 is equal to PVDD/N, with PVDD being a power supply voltage of the power amplifier output stage; and the noise control unit is a resistor module. The present application ensures the normal operation of the digital audio power amplifier.

A multi-frequency low noise amplifier includes an input matching network, an amplifying circuit and an output matching network. The input matching network includes a first out-of-band rejection circuit and a first frequency band selection circuit. The output matching network includes a second out-of-band rejection circuit and a second frequency band selection circuit. The first out-of-band rejection circuit can reject signal of any frequency band in the radio frequency signals so that signals of the remaining frequency bands can pass through. The first frequency band selection circuit can screen out the signals of reference frequency spots from the remaining frequency bands. The second frequency band selection circuit can screen out the signals of partial frequency spots from the amplified signals of reference frequency spots. The second out-of-band rejection circuit can reject the signal of any frequency spot in the signals of partial frequency spots.

A multi-frequency low noise amplifier includes an input matching network, an amplifying circuit and an output matching network. The input matching network includes a first out-of-band rejection circuit and a first frequency band selection circuit. The output matching network includes a second out-of-band rejection circuit and a second frequency band selection circuit. The first out-of-band rejection circuit can reject signal of any frequency band in the radio frequency signals so that signals of the remaining frequency bands can pass through. The first frequency band selection circuit can screen out the signals of reference frequency spots from the remaining frequency bands. The second frequency band selection circuit can screen out the signals of partial frequency spots from the amplified signals of reference frequency spots. The second out-of-band rejection circuit can reject the signal of any frequency spot in the signals of partial frequency spots.

An RF transceiver front end includes a receiver limb including a length of transmission line, an impedance matching network, a downstream shunt switch and a downstream further receiver component and a transmitter limb. The impedance matching network is configured to transform the input impedance of the further receiver component to match the input impedance of the receiver limb when the shunt switch is open and the RF transceiver front end is operable in receiver mode. The impedance matching network is further configured to transform the input impedance of the shunt switch to present an open circuit as the input impedance of the receiver limb when the shunt switch is closed and the RF transceiver front end is operable in transmitter mode. The length of transmission line can be from zero to less than λ/4 at the operating frequency of the RF transceiver.

An RF transceiver front end includes a receiver limb including a length of transmission line, an impedance matching network, a downstream shunt switch and a downstream further receiver component and a transmitter limb. The impedance matching network is configured to transform the input impedance of the further receiver component to match the input impedance of the receiver limb when the shunt switch is open and the RF transceiver front end is operable in receiver mode. The impedance matching network is further configured to transform the input impedance of the shunt switch to present an open circuit as the input impedance of the receiver limb when the shunt switch is closed and the RF transceiver front end is operable in transmitter mode. The length of transmission line can be from zero to less than λ/4 at the operating frequency of the RF transceiver.

A sensor assembly including a capacitive sensor, like a microelectromechanical (MEMS) microphone, and an electrical circuit therefor are disclosed. The electrical circuit includes a first transistor having an input gate connectable to the capacitive sensor, a second transistor having an input gate coupled to an output of the first transistor, a feedforward circuit interconnecting a back-gate of the second transistor and the output of the first transistor, and a filter circuit interconnecting the output of the first transistor and the input gate of the second transistor.