Amplifiers with wide input range and low input capacitance are provided. In certain embodiments, an amplifier input stage includes a pair of input terminals, a pair of n-type input transistors, a first pair of isolation switches connected between the input terminals and the n-type input transistors, a pair of p-type input transistors, and a second pair of isolation switches connected between the input terminals and the p-type input transistors. The amplifier input stage further includes a control circuit that determines whether to use the n-type input transistors and/or the p-type input transistors for amplification based on a detected common-mode voltage of the input terminals. The control circuit opens the first pair of isolation switches to decouple the input terminals from the n-type input transistors when unused, and opens the second pair of isolation switches to decouple the input terminals from the p-type input transistors when unused.

Amplifiers with wide input range and low input capacitance are provided. In certain embodiments, an amplifier input stage includes a pair of input terminals, a pair of n-type input transistors, a first pair of isolation switches connected between the input terminals and the n-type input transistors, a pair of p-type input transistors, and a second pair of isolation switches connected between the input terminals and the p-type input transistors. The amplifier input stage further includes a control circuit that determines whether to use the n-type input transistors and/or the p-type input transistors for amplification based on a detected common-mode voltage of the input terminals. The control circuit opens the first pair of isolation switches to decouple the input terminals from the n-type input transistors when unused, and opens the second pair of isolation switches to decouple the input terminals from the p-type input transistors when unused.

An amplifier for a receiver circuit is disclosed. The amplifier has an input node (V.sub.in) and an output node (V.sub.out). It comprises a tunable tank circuit connected to the output node (V.sub.out), a feedback circuit path connected between the output node (V.sub.out) and the input node (V.sub.in), and a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node. A receiver circuit and a communication apparatus is disclosed as well.

Chopper amplifiers with tracking of multiple input offsets are disclosed herein. In certain embodiments, a chopper amplifier includes chopper amplifier circuitry including an input chopping circuit, an amplification circuit, and an output chopping circuit electrically connected along a signal path. The amplification circuit includes two or more pairs of input transistors, from which a control circuit chooses a selected pair of input transistors to amplify an input signal. The chopper amplifier further incudes an offset correction circuit that senses the signal path to generate an input offset compensation signal for the amplification circuit. Furthermore, the offset correction circuit separately tracks an input offset of each of the two or more pairs of input transistors.

An operational amplifier integrated circuit includes a differential pair of transistors having a first input, a second input. A bias current generator applies a bias current to an output of the differential pair of transistors. A control loop generates a control voltage arising from a difference in potentials between the first input and the second input. An additional current that is added to the bias current is generated in response to the control voltage.

An amplifier for a receiver circuit is disclosed. The amplifier has an input node (V.sub.in) and an output node (V.sub.out). It comprises a tunable tank circuit connected to the output node (V.sub.out), a feedback circuit path connected between the output node (V.sub.out) and the input node (V.sub.in), and a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node. A receiver circuit and a communication apparatus is disclosed as well.

An amplifier for a receiver circuit is disclosed. The amplifier has an input node (V.sub.in) and an output node (V.sub.out). It comprises a tunable tank circuit connected to the output node (V.sub.out), a feedback circuit path connected between the output node (V.sub.out) and the input node (V.sub.in), and a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node. A receiver circuit and a communication apparatus is disclosed as well.

An operational amplifier integrated circuit includes a differential pair of transistors having a first input, a second input. A bias current generator applies a bias current to an output of the differential pair of transistors. A control loop generates a control voltage arising from a difference in potentials between the first input and the second input. An additional current that is added to the bias current is generated in response to the control voltage.

An amplifier for a receiver circuit is disclosed. The amplifier has an input node (V.sub.in) and an output node (V.sub.out). It comprises a tunable tank circuit connected to the output node (V.sub.out), a feedback circuit path connected between the output node (V.sub.out) and the input node (V.sub.in), and a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node. A receiver circuit and a communication apparatus is disclosed as well.

An amplifier for a receiver circuit is disclosed. The amplifier has an input node (V.sub.in) and an output node (V.sub.out). It comprises a tunable tank circuit connected to the output node (V.sub.out), a feedback circuit path connected between the output node (V.sub.out) and the input node (V.sub.in), and a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node. A receiver circuit and a communication apparatus is disclosed as well.