An amplifier for headphones including a current digital-to-analog converter (DAC) configured to output a current based on a digital audio input signal, an output electrically connected to a speaker and configured to output an output signal to the speaker, and a pulse width modulation (PWM) loop configured to receive an error signal, the error signal based on a difference between the current from the current DAC and a current of the output signal, and generate the output signal based on the error signal. The PWM loop includes an analog-to-digital converter (ADC) configured to receive an analog signal based on the current from the current DAC and output a digital signal representing the analog signal, and an encoder configured to receive the digital signal and output a pulse having a width based on the analog signal.

A voltage regulator and a power supply are provided. The voltage regulator includes an operational amplifier and an offset voltage control module. The offset voltage control module includes one or more stages of regulation branches connected in parallel, and controls an offset voltage of the operational amplifier with the one or more stages of regulation branches to regulate the output voltage. The offset voltage control module also includes a bandgap reference generation circuit, configured to generate a reference voltage irrelevant to a temperature coefficient that is received by the operational amplifier from the input terminal, wherein the bandgap reference generation circuit comprises at least one of: a V.sub.GS-based bandgap reference generation circuit having a full CMOS reference offset structure, a PTAT unit-based and V.sub.GS-based bandgap reference generation circuit having a full CMOS reference offset structure, and a PTAT unit-based and BJT-based bandgap reference generation circuit having a complementary structure.

A voltage regulator and a power supply are provided. The voltage regulator includes an operational amplifier and an offset voltage control module. The operational amplifier includes an input terminal and an output terminal, and is configured to generate an output voltage to be output from the output terminal based on a reference voltage received from the input terminal. The offset voltage control module includes one stage of regulation branch or more stages of regulation branches connected in parallel, and is configured to control an offset voltage of the operational amplifier based on selection of the regulation branch to regulate the output voltage. Since sine each stage of regulation branch in the offset voltage control module is based on a transistor structure, as compared with the voltage dividing resistor in the related art, the transistor has lower power consumption, and thus power consumption of the voltage regulator is lowered.

A voltage regulator and a power supply are provided. The voltage regulator includes an operational amplifier and an offset voltage control module. The operational amplifier includes an input terminal and an output terminal, and is configured to generate an output voltage to be output from the output terminal based on a reference voltage received from the input terminal. The offset voltage control module includes one stage of regulation branch or more stages of regulation branches connected in parallel, and is configured to control an offset voltage of the operational amplifier based on selection of the regulation branch to regulate the output voltage. Since sine each stage of regulation branch in the offset voltage control module is based on a transistor structure, as compared with the voltage dividing resistor in the related art, the transistor has lower power consumption, and thus power consumption of the voltage regulator is lowered.

A signal processing device is configured to compensate for process and temperature variations deviating from a nominal process and temperature condition. A transconductance amplifier circuit produces a current output dependent on a voltage input and a transconductance gain. A transimpedance amplifier circuit produces a voltage output dependent on the current. A bias circuit comprises transistors (M.sub.1, M.sub.2) configured such that the gate and drain of the first transistor (M.sub.1) are connected to the gate of the second transistor (M.sub.2) and to a PTAT current source. The source of the first transistor (M.sub.1) is connected to a node via a first resistor (R.sub.1), and the source of the second transistor (M.sub.2) is connected to that node via a second, trimmable resistor (R.sub.2). A feedback circuit for the transimpedance amplifier comprises a third, trimmable resistor (R.sub.3). The ratio between a resistance of the second and third resistors (R.sub.2, R.sub.3) is constant.

Embodiments of a method for amplifier calibration and an amplifier system are described. In one embodiment, a method for amplifier calibration involves amplifying an input signal using a first amplifier connected between an input terminal and an output terminal to generate an output signal and digitally performing offset calibration on a second amplifier coupled in parallel with the first amplifier between the input terminal and the output terminal while amplifying the input signal using the first amplifier. Other embodiments are also described.

A sample and hold circuit providing rail-to rail equivalent output is described. The circuit includes a sample and hold amplifier containing two separate sets of sampling capacitors, one set is coupled to a PMOS transistor differential stage and the other set is coupled to an NMOS transistor differential stage. The differential stages drive a current mirror based push-pull output differential stage to provide an output signal with ranges equivalent to a rail-to rail output signal swing.

An integrated circuit (IC) chip can include an operational amplifier with adjustable operational parameters. The IC chip can also include a trimming module configured to measure an output voltage of the operational amplifier in response to at least one of detecting that the operational amplifier has a positive supply voltage set to a level greater than a predetermined level and detecting a given common mode voltage at inverting and non-inverting inputs of the operational amplifier. The trimming module can also be configured to adjust the operational parameters of the operational amplifier based on the output voltage to trim the operational amplifier.

An integrated circuit (IC) chip can include an operational amplifier with adjustable operational parameters. The IC chip can also include a trimming module configured to measure an output voltage of the operational amplifier in response to at least one of detecting that the operational amplifier has a positive supply voltage set to a level greater than a predetermined level and detecting a given common mode voltage at inverting and non-inverting inputs of the operational amplifier. The trimming module can also be configured to adjust the operational parameters of the operational amplifier based on the output voltage to trim the operational amplifier.

A sample and hold circuit providing rail-to rail equivalent output is described. The circuit includes a sample and hold amplifier containing two separate sets of sampling capacitors, one set is coupled to a PMOS transistor differential stage and the other set is coupled to an NMOS transistor differential stage. The differential stages drive a current mirror based push-pull output differential stage to provide an output signal with ranges equivalent to a rail-to rail output signal swing.