A current reuse type FET amplifier according to the present invention has a capacitance provided between a drain of a first FET in a first stage and a gate of a second FET in a next stage, electrically separates a gate voltage of the second FET from a drain voltage of the first FET, and includes a control circuit controlling the gate voltage of the first FET and the gate voltage of the second FET so that a variation of a drain current of the second FET and a variation of a drain voltage of the first FET are reduced in accordance with a variation of a saturation current Idss of the FET. Furthermore, the current reuse type FET amplifier according to the present invention uses only a depression mode FET to provide a circuit configuration operable with a positive single power source.

A CMOS trans-impedance amplifier includes an inverting amplifier circuit and a feedback resistor. The inverting amplifier circuit includes an input end and an output end, and the feedback resistor is coupled therebetween. The inverting amplifier circuit includes at least three sequentially-connected amplifier units, and each amplifier unit includes at least three sequentially-connected nFETs, namely an input signal receiving part nFET, an intermediate part nFET and a DC signal receiving part nFET. A common connection terminal of the input signal receiving part nFET and the intermediate part nFET is configured to output an amplified voltage signal.

A transconductance circuit comprises a first transistor, a second transistor, a first source-degeneration device, a second source-degeneration device, a first feedback device, and a second feedback device. The gate node of the first transistor is coupled to a source node of the second transistor via the first feedback device. The gate node of the second transistor is coupled to a source node of the second transistor via the second feedback device. The source node of the first transistor is coupled to a reference voltage via the first source-degeneration device. The source node of the second transistor is coupled to the reference voltage via the second source-degeneration device.

In an embodiment, a differential buffer may include a first input stage that compares a non-inverting portion of an input signal alternately to a non-inverting portion of an output and to an inverting portion of the output. Another embodiment of the differential buffer may also include a second input stage that compares the inverting portion of the input signal alternately to the inverting portion of the output signal and to the non-inverting portion of the output signal. Other embodiments of the differential buffer may include a feedback chopper switch that transfers the non-inverting portion of the output signal and the inverting portion of the output signal to the first input stage and to the second input stage.

A circuit including an amplifier having an input and an output; and a feedback path comprising a transmission line electrically coupled or electrically connected to the output and the input. A low noise amplifier including the circuit wherein the feedback path cancels noise generated in the low noise amplifier.

An amplifier includes a first capacitor connected between an input node and a floating node, a second capacitor connected between the floating node and an output node, an amplifying element connected between a power supply voltage and the output node and operating in response to a voltage level of the floating node, a current bias source connected between the output node and a ground voltage, a first reset switch connected between the floating node and an intermediate node and operating in response to a reset bias, a second reset switch connected between the intermediate node and the output node and operating in response to the reset bias, and a reset bias generator circuit that outputs the reset bias in response to a reset signal. The reset bias is one of a reset voltage of the intermediate node, the power supply voltage, and the ground voltage.

Aspects of this disclosure relate to an impedance transformation circuit for use in an amplifier, such as a low noise amplifier. The impedance transformation circuit includes a matching circuit including a first inductor. The impedance transformation circuit also includes a second inductor. The first and second inductors are magnetically coupled to each other to provide negative feedback to linearize the amplifier.

A power amplifier, for a transmitter circuit is disclosed, which comprises at least one field-effect transistor having a gate terminal and a bulk terminal. The at least one field-effect transistor is configured to receive an input voltage at the gate terminal and a dynamic bias voltage at the bulk terminal. The power amplifier comprises a bias-voltage generation circuit configured to generate the dynamic bias voltage as a nonlinear function of an envelope of input signal. The input voltage is a linear function of the input signal. The bias-voltage generation circuit comprises a rectifier circuit configured to generate a rectified input voltage and an amplifier circuit, operatively connected to the rectifier circuit, configured to generate the dynamic bias voltage based on the rectified input voltage. The amplifier circuit is a variable-gain amplifier circuit and the power amplifier comprises a control circuit configured to tune the gain of the amplifier circuit.

An amplifier, comprising: an amplifying element having an input side and an output side; a first transformer on the output side of the amplifying element arranged to mutually couple a fraction of the output current from the amplifying element onto the input side of the amplifying element; a second transformer on the input side of the amplifying element arranged to increase the input voltage on the input side via mutual coupling of its primary and secondary windings; wherein a primary winding of the first transformer is connected to an output of the amplifying element; wherein a secondary winding of the first transformer is ac connected to a secondary winding of the second transformer; and wherein the primary winding of the first transformer is dc blocked from the secondary winding of the second transformer. The negative and the positive reactive feedback loops are not formed from the same trifilar transformer.

A low noise amplifier (LNA) includes a pair of n-type transistors, each configured to provide a first transconductance; a pair of p-type transistors, each configured to provide a second transconductance; a first pair of coupling capacitors, cross-coupled between the pair of n-type transistors, and configured to provide a first boosting coefficient to the first transconductance; and a second pair of coupling capacitors, cross-coupled between the pair of p-type transistors, and configured to provide a second boosting coefficient to the second transconductance, wherein the LNA is configured to use a boosted effective transconductance based on the first and second boosting coefficients, and the first and second transconductances to amplify an input signal.