An operational amplifier includes a differential input stage that amplifies a differential input signal to generate an intermediate signal; an amplification stage including an output transistor that is connected between an output terminal and a fixed voltage line, and is driven according to the intermediate signal; and an assist circuit, wherein the assist circuit includes: a first transistor connected in parallel with the output transistor; and a drive circuit that drives the first transistor according to a gate voltage of the output transistor.

Various methods and circuital arrangements for biasing gates of stacked transistor amplifier that includes two series connected transistor stacks of different polarities are presented, where the amplifier is configured to operate according to different modes of operation. Such circuital arrangements operate in a closed loop with a feedback error voltage that is based on a sensed voltage at a common node of the two series connected transistor stacks. According to one aspect, gate biasing voltages to input transistors of each of the two series connected stacks are adjusted by respective current mirrors that are controlled based on the feedback error voltage. According to another aspect, other gate biasing voltages are generated by maintaining a fixed gate biasing voltage between any two consecutive gate basing voltages.

Various methods and circuital arrangements for biasing gates of stacked transistor amplifier that includes two series connected transistor stacks of different polarities are presented, where the amplifier is configured to operate according to different modes of operation. Such circuital arrangements operate in a closed loop with a feedback error voltage that is based on a sensed voltage at a common node of the two series connected transistor stacks. According to one aspect, gate biasing voltages to input transistors of each of the two series connected stacks are adjusted by respective current mirrors that are controlled based on the feedback error voltage. According to another aspect, other gate biasing voltages are generated by maintaining a fixed gate biasing voltage between any two consecutive gate basing voltages.

A slew rate acceleration circuit in a buffer circuit, is configured at least to detect a current flowing through a load stage of the buffer circuit, compare a value of the detected current with a reference value, and supply an adjusting driving voltage to an output stage of the buffer circuit based on results of the comparison for increasing a slew rate of the buffer circuit.

Various methods and circuital arrangements for biasing gates of stacked transistor amplifier that includes two series connected transistor stacks of different polarities are presented, where the amplifier is configured to operate according to different modes of operation. Such circuital arrangements operate in a closed loop with a feedback error voltage that is based on a sensed voltage at a common node of the two series connected transistor stacks. According to one aspect, gate biasing voltages to input transistors of each of the two series connected stacks are adjusted by respective current mirrors that are controlled based on the feedback error voltage. According to another aspect, other gate biasing voltages are generated by maintaining a fixed gate biasing voltage between any two consecutive gate basing voltages.

The present invention discloses a hysteresis comparator comprising an input stage, a hysteresis current generating circuit and an output stage. In the operation of the hysteresis comparator, the input stage is configured to receive a pair of differential input signals to generate at least one differential current signal; the hysteresis current generating circuit is configured to generate at least one hysteresis current to adjust the differential current signal to generate an adjusted differential current signal, wherein the hysteresis current generating circuit includes a common mode voltage detecting circuit for detecting a common mode voltage of the differential input signal for generating the hysteresis current; and the output stage is configured to generate an output signal according to the adjusted differential current signal.

The present invention discloses a hysteresis comparator comprising an input stage, a hysteresis current generating circuit and an output stage. In the operation of the hysteresis comparator, the input stage is configured to receive a pair of differential input signals to generate at least one differential current signal; the hysteresis current generating circuit is configured to generate at least one hysteresis current to adjust the differential current signal to generate an adjusted differential current signal, wherein the hysteresis current generating circuit includes a common mode voltage detecting circuit for detecting a common mode voltage of the differential input signal for generating the hysteresis current; and the output stage is configured to generate an output signal according to the adjusted differential current signal.

Various methods and circuital arrangements for biasing gates of stacked transistor amplifier that includes two series connected transistor stacks of different polarities are presented, where the amplifier is configured to operate according to different modes of operation. Such circuital arrangements operate in a closed loop with a feedback error voltage that is based on a sensed voltage at a common node of the two series connected transistor stacks. According to one aspect, gate biasing voltages to input transistors of each of the two series connected stacks are adjusted by respective current mirrors that are controlled based on the feedback error voltage. According to another aspect, other gate biasing voltages are generated by maintaining a fixed gate biasing voltage between any two consecutive gate basing voltages.

A slew rate acceleration circuit in a buffer circuit, is configured at least to detect a current flowing through a load stage of the buffer circuit, compare a value of the detected current with a reference value, and supply an adjusting driving voltage to an output stage of the buffer circuit based on results of the comparison for increasing a slew rate of the buffer circuit.