A balanced differential transimpedance amplifier with a single-ended input operational over a wide variation in the dynamic range of input signals. A threshold circuit is employed to either or a combination of (1) generate a varying decision threshold to ensure a proper slicing over a wide range of input current signal levels; and (2) generate a bias current and voltage applied to an input of a transimpedance stage to cancel out a dependence of the transimpedance stage voltage input on input current signal levels.

A circuit includes a first operational amplifier having an inverting input and a non-inverting input, and a negative resistance circuit connected to the inverting input of the operational amplifier. The negative resistance circuit includes a second operational amplifier, a current source controlled by the second operational amplifier, and a cross-coupled transistor circuit having at least one transistor biased by a current produced by the current source.

A magnetic operational amplifier having a differential stage includes a first magnetic field effect transistor MAGFET and a differential signal conditioner, the differential signal conditioner including a load stage, a differential input pair connected to the load stage and a biasing current source connected to the differential input pair; the magnetic field effect transistor MAGFET being connected to the load stage as a second differential input pair and the differential signal conditioner including a second biasing current source connected to the magnetic field effect transistor MAGFET.

A circuit includes a first operational amplifier having an inverting input and a non-inverting input, and a negative resistance circuit connected to the inverting input of the operational amplifier. The negative resistance circuit includes a second operational amplifier, a current source controlled by the second operational amplifier, and a cross-coupled transistor circuit having at least one transistor biased by a current produced by the current source.

An impedance measurement circuit for determining a sense current of a guard-sense capacitive sensor operated in loading mode. The circuit includes a periodic signal voltage source for providing a periodic measurement voltage, a sense current measurement circuit, a differential amplifier that is configured to sense a complex voltage difference between the sense electrode and the guard electrode, a demodulator for obtaining, with reference to the periodic measurement voltage, an in-phase component and a quadrature component of the sensed complex voltage difference, and control loops for receiving the in-phase component and the quadrature component, respectively. An output signal of the first control loop and an output signal of the second control loop are usable to form a complex voltage that serves as a complex reference voltage for the sense current measurement circuit.

The invention relates to an amplification circuit (100), comprising: a VGA (2), an AGC loop (10) for automatically controlling the gain of the VGA (2), a switching circuit (14) for switching between an AGC mode, in which the gain of the VGA (2) is automatically controlled by an output signal of the AGC loop (10) and a manual gain control, MGC, mode, in which the gain of the VGA (2) can be manually controlled by an input signal, and a read/write circuit (30) with a contact (31) for connection to a peripheral system, wherein the read/write circuit (30) is configured, in the MGC mode, to provide the input signal from the contact (31) via a write-mode path (32) to the VGA (2), and, in the AGC mode, to provide the output signal of the AGC loop (10) via a read-mode path (33) on the contact (31).

A drive circuit for a serial communications system is provided. The drive circuit may include a mode controller, a pre-drive circuit, and a main drive circuit. The main drive circuit includes multiple mode control switches and at least one pair of differential switches. The mode controller is configured to: generate a mode control signal, and transmit the mode control signal to the main drive circuit. The pre-drive circuit is configured to: convert a differential digital signal into a differential control signal, and transmit the differential control signal to the main drive circuit. The main drive circuit controls on/off states of the multiple mode control switches according to the mode control signal, and works in corresponding working modes. The drive circuit controls the states of the mode control switches in the main drive circuit, so that the main drive circuit works in different working modes.

A magnetic operational amplifier having a differential stage includes a first magnetic field effect transistor MAGFET and a differential signal conditioner, the differential signal conditioner including a load stage, a differential input pair connected to the load stage and a biasing current source connected to the differential input pair; the magnetic field effect transistor MAGFET being connected to the load stage as a second differential input pair and the differential signal conditioner including a second biasing current source connected to the magnetic field effect transistor MAGFET.

The invention relates to an amplification circuit (100), comprising: a VGA (2), an AGC loop (10) for automatically controlling the gain of the VGA (2), a switching circuit (14) for switching between an AGC mode, in which the gain of the VGA (2) is automatically controlled by an output signal of the AGC loop (10) and a manual gain control, MGC, mode, in which the gain of the VGA (2) can be manually controlled by an input signal, and a read/write circuit (30) with a contact (31) for connection to a peripheral system, wherein the read/write circuit (30) is configured, in the MGC mode, to provide the input signal from the contact (31) via a write-mode path (32) to the VGA (2), and, in the AGC mode, to provide the output signal of the AGC loop (10) via a read-mode path (33) on the contact (31).

An operational amplifier and a differential amplifying circuit thereof. The differential amplifying circuit receives a differential input signal and outputs a differential output signal. The differential amplifying circuit includes an output port that has a first terminal and a second terminal, the differential output signal being outputted via the first and second terminals; a first transistor pair receiving the differential input signal via two first ends and coupling to the first and second terminals respectively via two second ends; a second transistor pair receiving the differential input signal via two first ends and coupling to the first and second terminals respectively via two second ends; and a third transistor pair receiving a control signal via two first ends and coupling to the first and second terminals respectively via two second ends. The control signal controls the third transistor pair to switch on or off and/or controls the current flowing therethrough.