A dynamic differential amplifier includes: gain transistors to drive with differential input voltage levels; sample capacitors having first terminals to ramp from an initial voltage level to differential amplified voltage levels of the input voltage levels in response to the driven gain transistors; and adjustment circuits to adjust the amplified voltage levels in the direction of the initial voltage level by an offset voltage level. In some cases, second terminals of the sample capacitors are a common-mode node to maintain a common-mode voltage level midway between the ramping voltage levels of the first terminals. In some cases, the dynamic differential amplifier further includes a comparison circuit to compare the maintained common-mode voltage level to a threshold voltage level, wherein the first terminals of the sample capacitors stop ramping and the adjustment circuits adjust the amplified voltage levels in response to the compared common-mode voltage level reaching the threshold voltage level.

Various embodiments of the present technology comprise a method and apparatus for a dual mode operational amplifier. According to various embodiments, the operational amplifier functions as both a fully-differential amplifier and a single-ended amplifier. The operational amplifier may comprise additional transistors that function as switches, which can be selectively operated according to a desired mode.

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.

An operational amplifier circuit is provided. The operational amplifier circuit includes a differential input stage circuit and a loading stage circuit. The differential input stage circuit includes an input circuit, a voltage maintaining circuit, and a current source. The input circuit includes a first input transistor and a second input transistor, for receiving a first and a second input signals, respectively. The voltage maintaining circuit includes a first branch circuit and a second branch circuit. The first branch circuit is coupled to the first input transistor for receiving the first input signal, and the second branch circuit is coupled to the second input transistor for receiving the second input signal. The current source is coupled to the first input transistor and the second input transistor. The loading stage circuit is coupled to the voltage maintaining circuit.

A voltage driver circuit for an output stage of an operational amplifier, or other circuits, includes a level shifter and an output driver including a source follower and a common source amplifier in a push-pull configuration. The level shifter generates a node voltage as a function of an input voltage on the input node. The output driver including a first transistor having a control terminal receiving the node voltage, and connected between a supply voltage and an output node, and a second transistor having a control terminal receiving the input voltage from the input node, and connected between the output node and a reference voltage, wherein the first and second transistors have a common conductivity type.

A amplifier circuit in some embodiment includes a differential amplifier have a pair of current sources. Each of the current sources includes two or more current-generating transistors and respective switching transistors, which can be turned on and off by a gain input code to tune the gain of the amplifier. A common-mode controller includes a similar pair of current sources as the differential amplifier. The common mode controller receives a common-mode signal of the input signal and a common-mode gain input code, and maintains the common-mode gain of the amplifier circuit when the differential gain changes. The amplifier circuit is switchable between a buffer mode and an equalizer mode.

A current regulator and a method for regulating a current flowing through a device such as a semiconductor light source is presented. The current regulator has a voltage controller coupled to a current steering circuit. The voltage controller is adapted to operate the current steering circuit in a linear mode.

Methods and systems are described for receiving, at an input differential branch pair, a set of input signals, and responsively generating a first differential current, receiving, at an input of an offset voltage branch pair, an offset voltage control signal, and responsively generating a second differential current, supplementing a high-frequency component of the second differential current by injecting a high-pass filtered version of the set of input signals into the input of the offset voltage branch pair using a high-pass filter, and generating an output differential current based on the first and second differential currents using an amplifier stage connected to the input differential branch pair and the offset voltage branch pair.

An integrated circuit includes: a first differential buffer suitable for receiving a primary signal through a primary input terminal thereof, and receiving a secondary signal through a secondary input terminal thereof, wherein the secondary signal has a phase opposite to a phase of the primary signal; a second differential buffer suitable for receiving a first reference voltage through primary and secondary input terminals thereof; and an operational amplifier suitable for receiving a first common mode voltage of the primary and secondary output terminals of the first differential buffer and a second common mode voltage of the primary and secondary output terminals of the second differential buffer, to output the first reference voltage.

An apparatus for performing baseline wander correction is provided. The apparatus may include: a plurality of filters, a common mode voltage generator, and a compensation circuit. The plurality of filters may filter a set of input signals to generate a set of differential signals, the common mode voltage generator may generate a common mode voltage between the set of differential signals, and the compensation circuit may perform compensation related to baseline wander correction on the set of differential signals. Multiple current paths of the compensation circuit are associated with each other. Through a first current path and a second current path within the current paths, the compensation circuit may perform charge or discharge control on a first capacitor and a second capacitor within the plurality of filters to dynamically adjust compensation amounts of the compensation, to reduce or eliminate a baseline wander effect of the set of differential signals.