The present invention provides a circuit having a filter with an amplifier circuit for filtering and amplifying an input signal to generate an output signal, wherein a corner frequency of the filter is adjustable to control a settling time of the output signal.

Techniques for monitoring a distortion signal of a power amplifier circuit, where the output of a distortion monitoring circuit includes little or no fundamental signal and closely represents the actual distortion of the amplifier circuit of a wired communications system. The power amplifier circuit can generate a distortion feedback signal that does not affect the power amplifier's output power capability, e.g., no inherent loss in the fundamental output of the amplifier. That is, using a distortion monitor circuit, the power amplifier circuit can resolve a distortion feedback signal from the intended output signal of the output power amplifier circuit.

According to one embodiment, a compact low-power receiver comprises first and second analog circuits connected by a digitally controlled interface circuit. The first analog circuit has a first direct-current (DC) offset and a first common mode voltage at an output, and the second analog circuit has a second DC offset and a second common mode voltage at an input. The digitally controlled interface circuit connects the output to the input, and is configured to match the first and second DC offsets and to match the first and second common mode voltages. In one embodiment, the first analog circuit is a variable gain control transimpedance amplifier (TIA) implemented using a current mode buffer, the second analog circuit is a second-order adjustable low-pass filter, whereby a three-pole adjustable low-pass filter in the compact low-power receiver is effectively produced.

Low-power, high-performance voltage regulator circuit devices are disclosed and described. In one embodiment, such a device can include a first stage circuitry configured to generate a high voltage reference from a low voltage reference, a second stage circuitry coupled to the first stage circuitry, the second stage circuitry configured to receive the high voltage reference and output a voltage regulated signal, and a switch disposed between and coupled to the first stage circuitry and the second stage circuitry, the switch being configured to couple and uncouple the first stage circuitry from the second stage circuitry.

An amplifier circuit includes a converter configured to convert a predefined physical quantity to a resistance value, and the resistance value converted by the converter is converted to a voltage value and then amplified. The converter includes variable resistance sensors of piezoresistance elements. A bias unit is configured to determine a bias current of the converter, and includes bias resistances. An operation amplifier unit receives, as input signals, output signals from the bias unit and the converter, and includes feedback resistances respectively connected to input and output ends of a first operational amplifier. The first operational amplifier is a whole differential operational amplifier including a common-mode feedback circuit.

Low-power, high-performance voltage regulator circuit devices are disclosed and described. In one embodiment, such a device can include a first stage circuitry configured to generate a high voltage reference from a low voltage reference, a second stage circuitry coupled to the first stage circuitry, the second stage circuitry configured to receive the high voltage reference and output a voltage regulated signal, and a switch disposed between and coupled to the first stage circuitry and the second stage circuitry, the switch being configured to couple and uncouple the first stage circuitry from the second stage circuitry.

An operational amplifier based circuit has an operational amplifier, a feedback circuit, and a compensation circuit block. The feedback circuit is coupled between an output port and an input port of the operational amplifier. The compensation circuit block has circuits involved in stability compensation of the operational amplifier, wherein there is no stability compensation circuit driven at the output port of the operational amplifier.

An amplifier with adjustable gain including a plurality of differential amplifiers and an output stage circuit is provided. Each of the differential amplifiers has at least one differential pair, two current terminals of each of the differential pairs are coupled by a connection structure, and the connection structure provides a negative feedback resistance. The differential amplifiers commonly receive a differential input signal pair, and output terminals of the differential amplifiers are coupled together. The output stage circuit inverts a voltage on the output terminals of the differential amplifiers to generate an output voltage. A direct current gain of the amplifier with adjustable gain is determined by adjusting at least one of working numbers of the differential amplifiers and the differential pairs.

An amplifier with adjustable gain including a plurality of differential amplifiers and an output stage circuit is provided. Each of the differential amplifiers has at least one differential pair, two current terminals of each of the differential pairs are coupled by a connection structure, and the connection structure provides a negative feedback resistance. The differential amplifiers commonly receive a differential input signal pair, and output terminals of the differential amplifiers are coupled together. The output stage circuit inverts a voltage on the output terminals of the differential amplifiers to generate an output voltage. A direct current gain of the amplifier with adjustable gain is determined by adjusting at least one of working numbers of the differential amplifiers and the differential pairs.

An instrumentation amplifier includes first and second resistors for gain setting. The operational amplifiers within the instrumentation amplifier include selectively enabled current drive sources coupled to the amplifier output. The first and second resistors have variable resistances. A control circuit is configured to select the variable resistances of the first and second resistors to implement a fixed gain for the instrumentation amplifier and further selectively enable the current drive sources. The control circuit receives an indication of a downstream programmable gain (for example, from a downstream programmable gain amplifier). The variable resistances of the first and second resistors are selected to be scaled inversely with respect to the downstream programmable gain and the current drive sources are enabled proportionately with respect to the downstream programmable gain.