A switching converter includes a voltage conversion circuit providing an output voltage from an input voltage and a PWM voltage generated in response to first and second oscillating voltages. The input stage of a transconductor circuit provides an input reference current following a difference between a reference voltage and a voltage dependent on the output voltage and according to a transconductance, and an output stage for providing an output reference current from the input reference current. A phase shifter shifts an oscillating reference voltage according to the output reference current to obtain the first and second oscillating voltages. The transconductance is controlled in response to the input voltage resulting in a change of the input reference current. Compensation for that change is provided by subtracting a variable compensation current from the input reference current, where the variable compensation current is generated in response to the input voltage.

A buffer circuit includes a first differential amplifier, second differential amplifier, third differential amplifier, and mixer. The first differential amplifier generates a positive differential signal and a negative differential signal based on an input signal and a reference voltage signal. The second differential amplifier generates a first signal based on the positive differential signal and the negative differential signal. The third differential amplifier generates a second signal having a different phase from the first signal based on the positive differential signal and the negative differential signal. The mixer outputs a signal, generated by mixing the first signal and the second signal, as an output signal.

A voltage generation circuit may include: a first transistor coupled to an internal supply voltage terminal, and configured as a diode-connected transistor; a second transistor coupled to the first transistor and configured as a diode-connected transistor; and a third transistor coupled between the second transistor and a ground voltage terminal, and configured to operate according to a first reference voltage generated based on an external supply voltage. The voltage generation circuit may limit a variation in level of a second reference voltage which is generated through a drain terminal of the second transistor as a threshold voltage of the second transistor rises according to a rise in level of the internal supply voltage.

Apparatus and methods for reducing input bias current of electronic circuits are provided herein. In certain implementations, an electronic circuit includes a first input terminal, a second input terminal, an input circuit, and a plurality of input switches including at least a first input switch and a second input switch. The first input switch is electrically connected between the first input terminal and a first input of the input circuit, the second input switch is electrically connected between the second input terminal and a second input of the input circuit, and the first and second input switches can be opened and closed using a clock signal. The electronic circuit further includes a charge compensation circuit for compensating for charge injection through the first and second input switches during transitions of the clock signal.

Linearity is improved in an amplifier circuit without lowering gain. The amplifier circuit includes a transistor, a load, an impedance element, and a variable current source. The transistor amplifies an input signal. The load is connected between the transistor and a power supply. The impedance element is connected between the transistor and a ground terminal, and passes a direct current. The variable current source is connected to a connection part between the transistor and the impedance element, and supplies a current in accordance with a voltage of the connection part.

A differential amplifier circuit includes: a control current source supplying a control current; paired bipolar transistors; an a variable resistance circuit including: a series circuit of a first resistor and a second resistor having an identical resistance, the series circuit electrically connected between a first terminal and a second terminal of the variable resistance circuit; a first field effect transistor (FET) having a source and a drain being electrically connected to emitters of the paired bipolar transistors, respectively; and a second FET having a drain, a gate being electrically connected to the drain thereof, the gate of the first FET, and a control terminal of variable resistance circuit, a source being electrically connected to a connection node between the first resistor and the second resistor, wherein the control current source adjusts the control current to allow transconductance of the second FET to be kept constant.

Disclosed is an operational amplifier, including a first-stage gain circuit, a second-stage gain circuit, and a tail current compensation circuit. The first-stage gain circuit is connected to the second-stage gain circuit, the first-stage gain circuit is provided with an input terminal, the second-stage gain circuit is provided with an output terminal. The first-stage gain circuit at least includes a tail current source, a first terminal of the tail current compensation circuit is connected to the tail current source, and a second terminal of the tail current compensation circuit is connected to the output terminal of the second-stage gain circuit. The tail current compensation circuit is configured to compensate the tail current source with an output signal of the output terminal of the second-stage gain circuit.

A voltage generation circuit may include: a first transistor coupled to an internal supply voltage terminal, and configured as a diode-connected transistor; a second transistor coupled to the first transistor and configured as a diode-connected transistor; and a third transistor coupled between the second transistor and a ground voltage terminal, and configured to operate according to a first reference voltage generated based on an external supply voltage. The voltage generation circuit may limit a variation in level of a second reference voltage which is generated through a drain terminal of the second transistor as a threshold voltage of the second transistor rises according to a rise in level of the internal supply voltage.

Disclosed is an operational amplifier, including a first-stage gain circuit, a second-stage gain circuit, and a tail current compensation circuit. The first-stage gain circuit is connected to the second-stage gain circuit, the first-stage gain circuit is provided with an input terminal, the second-stage gain circuit is provided with an output terminal. The first-stage gain circuit at least includes a tail current source, a first terminal of the tail current compensation circuit is connected to the tail current source, and a second terminal of the tail current compensation circuit is connected to the output terminal of the second-stage gain circuit. The tail current compensation circuit is configured to compensate the tail current source with an output signal of the output terminal of the second-stage gain circuit.

A voltage generation circuit may include: a first transistor coupled to an internal supply voltage terminal, and configured as a diode-connected transistor; a second transistor coupled to the first transistor and configured as a diode-connected transistor; and a third transistor coupled between the second transistor and a ground voltage terminal, and configured to operate according to a first reference voltage generated based on an external supply voltage. The voltage generation circuit may limit a variation in level of a second reference voltage which is generated through a drain terminal of the second transistor as a threshold voltage of the second transistor rises according to a rise in level of the internal supply voltage.