Systems, methods and apparatus for efficient power control of an RF amplifier for amplification of a constant envelope RF signal are described. A reduction in a size of a pass device of an LDO regulator is obtained by removing the pass device of the LDO regulator from a main current conduction path of the RF amplifier. Power control is provided by varying one or more gate voltages to cascoded transistors of a transistor stack of the RF amplifier according to a power control voltage. Various configurations for controlling the gate voltages are presented by way of a smaller size LDO regulator or by completely removing the LDO regulator. In a case where a supply voltage to the transistor stack varies, such as in a case of a battery, a compensation circuit is used to adjust the power control voltage in view of a variation of the supply voltage, and therefore null a corresponding drift in output power of the RF amplifier.

A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.

One aspect of the present disclosure relates to a method for operating an amplifier, the amplifier including a variable resistor coupled between a source of a first input transistor and a source of a second input transistors, and a variable capacitor coupled between the source of the first input transistor and the source of the second input transistor. The method includes adjusting a resistance of the variable resistor to adjust a low-frequency gain of the amplifier, and adjusting a capacitance of the variable capacitor in an opposite direction as the adjustment to the resistance of the variable resistor.

The present invention is directed to electrical circuits and techniques thereof. More specifically, an embodiment of the present invention provides a variable gain amplifier that includes a first transistor and a second transistor whose gate terminals are coupled to a first input terminal. A first drain terminal of the first transistor and a first source terminal of the second transistor is coupled to a voltage gain control switch. There are other embodiments as well.

A Programmable-Gain Amplifier (PGA) has programming steps that are linear when expressed in Decibels (linear-in-dB). A Recursive Current Division (RCD) resistor network generates currents that are selected by programmable switches to connect to a summing node input of an amplifier. A feedback resistor is connected across the summing node and the amplifier output. The resistor network has only three resistance values regardless of the number of currents selectable as programming steps. The value of a third resistor is set equal to the equivalent resistance of a second resistor in parallel with a series connection of a first resistor and the third resistors. Each final cell in the resistor network is equivalent to the third resistor, allowing recursive division of adjacent currents. The ratio of adjacent currents remains constant for all cells. Recursive Current Division (RCD) produces linear-in-dB programming steps. Floating switches are avoided since switches connect to ground.

In accordance with an embodiment, an integrated circuit includes a substrate, an amplifier MOSFET, and a bias voltage terminal configured to generate a potential difference of the substrate relative to at least one load terminal of the amplifier MOSFET.

A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.

The present disclosure describes a method and system for linearizing an amplifier using transistor-level dynamic feedback. The method and system enables nonlinear amplifiers to exhibit linear performance using one or more of gain control elements and phase shifters in the feedback path. The disclosed method and system may also allow an amplifier to act as a pre-distorter or a frequency/gain programmable amplifier.

A method and electronic circuit for changing the gain of a radio frequency signal. The apparatus is an electronic circuit comprising one or more variable gain electronic elements, and one or more adjustable phase shifting elements. The method comprises the steps of receiving a radio frequency signal, varying the gain of the variable gain electronic element while the variable gain electronic element changes the amplitude of the radio frequency signal, and adjusting an adjustable phase shifting element to generate a reverse phase shift in the radio frequency signal in response to the associated phase shift from the step of varying the gain.

A method and electronic circuit for changing the gain of a radio frequency signal. The apparatus is an electronic circuit comprising one or more variable gain electronic elements, and one or more adjustable phase shifting elements. The method comprises the steps of receiving a radio frequency signal, varying the gain of the variable gain electronic element while the variable gain electronic element changes the amplitude of the radio frequency signal, and adjusting an adjustable phase shifting element to generate a reverse phase shift in the radio frequency signal in response to the associated phase shift from the step of varying the gain.