Disclosed herein is a method including sinking current from a pair of input transistors of a differential amplifier while sourcing more current to the pair of input transistors than is sunk. The method further includes generating a pair of input differential signals using a pair of input voltage regulators, and amplifying a difference between the pair of input differential signals to produce a pair of differential output voltages, using the differential amplifier. The method also includes amplifying the pair of differential output voltages using at least one voltage gain amplifier, and generating control signals for current sources that source the current to the pair of input transistors of the differential amplifier, from the pair of differential output voltages after at least amplification.

Provided is a track-and-hold circuit capable of reducing the power consumption of a differential amplifier circuit while preserving the broadband nature (without narrowing the bandwidth). In the track-and-hold circuit 1 including a differential amplifier circuit 10, a switch circuit 20, and a hold capacitor C.sub.21, the differential amplifier circuit 10 includes a first resistor R.sub.11 having one end connected to a collector electrode of a first transistor Q.sub.11 constituting a differential pair, a second resistor R.sub.12 having one end connected to the collector electrode of a second transistor Q.sub.12 constituting the differential pair, and a third resistor R.sub.13 to which the other end of the first resistor R.sub.11 and the other end of the second resistor R.sub.12 are connected and which is connected between the other ends and a power supply V.sub.CC.

Certain aspects of the present disclosure provide methods and apparatus for amplifying an input signal. One example apparatus is a differential amplifier that includes a positive input node, a negative input node, a positive output node, a negative output node, a positive input transistor having a gate coupled to the positive input node and having a drain coupled to the negative output node, a negative input transistor having a gate coupled to the negative input node and having a drain coupled to the positive output node, a first common-gate amplifier having an output coupled to the negative output node, a second common-gate amplifier having an output coupled to the positive output node, a first capacitive element coupled between the negative input node and an input of the first common-gate amplifier, and a second capacitive element coupled between the positive input node and an input of the second common-gate amplifier.

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.

A linear amplifier outputs differential signals corresponding to differential signals input to a first signal input terminal and a second signal input terminal, and includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, a third transistor, a fourth transistor, a differential amplifier, and a signal processing circuit. The signal processing circuit includes a first transistor and a second transistor, and includes a resistor as a common voltage output part that outputs a common voltage. The differential amplifier receives the common voltage and a reference voltage, and applies a voltage corresponding to the voltage difference between the common voltage and the reference voltage to the control terminals of the transistors.

A continuous time linear equalization (CTLE) circuit is disclosed. The CTLE circuit includes a passive CTLE circuit and an active CTLE circuit. The active CTLE circuit includes a differential transistor pair and the output of the passive CTLE is configured to drive gates or bases of the differential transistor pair.

A high bandwidth continuous time linear equalization (HBCTLE) circuit is disclosed. The HBCTLE circuit includes a continuous time linear equalization (CTLE) circuit and a gain circuit coupled with an output of the CTLE circuit. A feedback circuit is coupled between the output of the CTLE circuit and an output of the gain circuit.

A continuous time linear equalization (CTLE) circuit is disclosed. The CTLE circuit includes a passive CTLE circuit and an active CTLE circuit. The active CTLE circuit includes a differential transistor pair and the output of the passive CTLE is configured to drive gates or bases of the differential transistor pair.

A system includes an instrumentation amplifier (INA) including a first transistor coupled to a first input node, and a second transistor coupled to a second input node. The INA also includes a resistor coupled between the first transistor and the second transistor. The INA includes a gain resistor network coupled to the resistor and to the first and second transistors, where the gain resistor network includes two or more gain resistors. The system also includes a voltage to current converter, where the voltage to current converter is coupled to the resistor and the gain resistor network.

Disclosed herein is a method including sinking current from a pair of input transistors of a differential amplifier while sourcing more current to the pair of input transistors than is sunk. The method further includes generating a pair of input differential signals using a pair of input voltage regulators, and amplifying a difference between the pair of input differential signals to produce a pair of differential output voltages, using the differential amplifier. The method also includes amplifying the pair of differential output voltages using at least one voltage gain amplifier, and generating control signals for current sources that source the current to the pair of input transistors of the differential amplifier, from the pair of differential output voltages after at least amplification.