The present invention is directed to electrical circuits. In a specific embodiment, the present invention provides variable gain amplifier that includes an impedance ladder and a control circuit. The impedance ladder includes n switches configured in parallel. The control circuit includes a digital-to-analog converter and an amplifier. The control circuit generates n control signals for the n switches. There are other embodiments as well.

In one form, a signal chain circuit includes a signal chain processing circuit between an input for receiving a differential input signal having a first common-mode voltage, and an output for providing a differential output signal having a second, different common-mode voltage. It includes an amplifier with a differential output stage coupled to a differential input stage and having positive and negative output terminals forming its output, and positive and negative feedback terminals. The differential output stage provides a first voltage drop between the positive output terminal and the positive feedback terminal, and a second voltage drop between the negative output terminal and the negative feedback terminal. The common-mode feedback circuit regulates a common-mode voltage between the positive and negative feedback terminals to the second common-mode voltage. In another form, an analog-to-digital converter includes a range extending logic circuit to extend the range of a ring oscillator based analog-to-digital converter.

A precharge circuit comprises a gain amplifier, a comparator, a reservoir capacitor, a switch, a current source, and a switching network. The gain amplifier has a gain G1 and receives an input voltage Vrefp. The gain amplifier outputs an amplified voltage G1Vrefp to the comparator, which compares G1Vrefp to a voltage across the reservoir capacitor. The comparator outputs a control signal for the switch based on the comparison. The switch couples the current source to the reservoir capacitor. The current from the current source charges the reservoir capacitor. The switching network couples the reservoir capacitor to an output of the precharge circuit during a first operating mode and provides the input voltage Vrefp to the output during a second operating mode.

An analog front end (AFE) circuit including: a continuous time linear equalizer (CTLE) circuit; a transimpedance amplifier (TIA) connected to the CTLE circuit; and a feedback circuit including: a first transistor connected between a first output of the feedback circuit and a first node connected to a first current source; a second transistor connected between a second output of the feedback circuit and a second node connected to a second current source; and a first tunable resistor coupled between the first node and the second node, wherein: a first input of the feedback circuit is connected to a first output of the TIA; a second input of the feedback circuit is connected to a second output of the TIA; the second output of the feedback circuit is connected to a first input of the TIA.

A transimpedance amplifier is provided for converting a current between its two input terminals to a voltage over its two output terminals comprising a high-speed level shifter configured for creating a difference in input DC voltage and for being transparent for alternating voltages, an input biasing network configured for reverse biasing a photodiode connected to at least one of the input terminals and transparent for a feedback signal from the feedback network which is differentially and DC-coupled with the output terminals of the voltage amplifier and outputs of the feedback network are differentially and DC-coupled with the input biasing network of which outputs are coupled with inputs of the level shifter which is differentially and DC-coupled with input terminals of the voltage amplifier.

A fully differential rail-to-rail-output amplifier includes a differential input inverter pair, folded cascode pair, class AB control pair, and class AB output rail-to-rail pair. A drain associated with the folded cascode pair is operatively coupled to the class AB control pair, and the drain associated with the folded cascode pair is unconnected to the current source associated with the class AB control pair. A method of providing fully differential rail-to-rail-output amplification includes coupling a folded cascode pair operatively to a differential input inverter pair, coupling a drain associated with the folded cascode pair operatively to a class AB control pair, and coupling a class AB output rail-to-rail pair operatively to the class AB control pair.

A voltage-to-current converter circuit comprises an amplifier, a resistor, first and second feedback circuits, and an output circuit. The amplifier is configured to receive a differential input voltage signal. The resistor is coupled between first and second nodes of the amplifier. The first feedback circuit is coupled to a third node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a first range, and is turned off otherwise. The second feedback circuit is coupled to a fourth node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a second range different from the first range, and is turned off otherwise. The output circuit produces a differential current output signal having a value according to the value of the input voltage signal.

Disclosed herein is an operational amplifier including a non-inverting input terminal, an inverting input terminal, a P-type metal oxide semiconductor input differential pair, a first input tail current source, an N-type metal oxide semiconductor input differential pair, a second input tail current source, an output stage, a first correction circuit, and a second correction circuit. The first correction circuit and the second correction circuit operate over an operation region of the P-type metal oxide semiconductor input differential pair, an operation region of the N-type metal oxide semiconductor input differential pair, and a transition region in which both the P-type metal oxide semiconductor input differential pair and the N-type metal oxide semiconductor input differential pair operate.

An amplifier circuit has: a first amplifier circuit, including a chopper circuit amplifying a first differential signal input between first and second input terminals to output a second differential signal; and a second amplifier circuit amplifying the second differential signal to output a single-ended signal. The second amplifier circuit includes: a first circuit including first and second transistors, the first circuit being connected to the first amplifier circuit so that the second differential signal input into gates of these transistors, the first circuit converting the second differential signal to a current flowing into a first node connected to the first transistor and a current flowing into a second node connected to the second transistor; and a second circuit negatively feeding back a voltage at the second node so that the difference in voltage between these nodes is reduced. The second amplifier circuit outputs the single-ended signal from the first node.

A system may include a front end differential amplifier having two input terminals, two input resistors, each of the two input resistors coupled to a respective one of the two input terminals, and an input common mode biasing circuit for an output stage of the front end differential amplifier, the input common mode biasing circuit comprising two current sources configured to generate currents for biasing the output stage of the front end differential amplifier.