The present invention is directed to electrical circuits. More specifically, embodiments of the present invention provide a variable gain amplifier (VGA) device that includes a low-gain tuning section and a high-gain tuning section. The low-gain tuning section includes both resistor and transistor elements. The high-gain tuning section includes a transistor element and is activated when an output gain is greater than a predetermined threshold level. There are other embodiments as well.

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 is formed on an SOI. The bias generator is connected to the gates of first and second transistors. In the bias generator, a first variable current source is connected to the power supply circuit via a power supply node. A third transistor is connected between the first variable current source and a ground-voltage source. A gate thereof is connected to the gate of the first transistor. A first operational amplifier controls a gate voltage of the third transistor so that a voltage at a second node between the first variable current source and the third transistor becomes almost equal to a reference-voltage. A first characteristics changer is connected to the gate of the third transistor or a second node, to change at least one loop gain characteristics and phase characteristics of a loop from the first operational amplifier, through the third transistor, to the first variable current source.

A variable attenuator (v-ATT) is disclosed. The v-ATT includes an input terminal, an output terminal, a transmission line between the input and output terminals, at least two stages provided between the transmission line and the ground, and a bias unit. Each of the stages includes a field effect transistor (FET) that varies impedance between the transmission line and the ground according to a bias provided to the gate thereof. The bias unit generates the biases each provided to the stages. One of the features of the v-ATT is that at least one of the stages receives at least one of the biases that is different from biases provided to other of the at least one of the stages.

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.

An equalizer, in at least some embodiments, comprises an amplifier configured to produce an amplified voltage signal that is a function of an ambient temperature affecting the equalizer. The equalizer also includes a linear equalizer stage coupled to the amplifier and comprising a transistor having a resistance controlled by the amplified voltage signal. The linear equalizer stage is configured to produce a voltage output signal having a gain that is dependent on the transistor resistance and on a frequency of the amplified voltage signal.

The present invention is directed to electrical circuits. More specifically, embodiments of the present invention provide a variable gain amplifier (VGA) device that includes a low-gain tuning section and a high-gain tuning section. The low-gain tuning section includes both resistor and transistor elements. The high-gain tuning section includes a transistor element and is activated when an output gain is greater than a predetermined threshold level. There are other embodiments as well.

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 variable attenuation device includes: a first variable attenuator configured to receive a first signal through a first input end, attenuate the first signal by an amount of attenuation according to a control voltage, and output the attenuated first signal through a first output end, the first signal being one of a pair of differential signals having a 180-degree phase difference; a second variable attenuator configured to receive a second signal through a second input end, attenuate the second signal by the amount of attenuation according to the control voltage, and output the attenuated second signal through a second output end, the second signal being the other one of the pair of differential signals; a first signal distributer configured to distribute the second signal to the first output end; and a second signal distributer configured to distribute the first signal to the second output end.

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.