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.

The inventive concepts relate to variable gain amplifiers. The variable gain amplifier including an amplifier, a first fixed resistor and a first variable resistor, a second fixed resistor and a second variable resistor, a third fixed resistor and a third variable resistor, a fourth fixed resistor and a fourth variable resistor, a first output terminal and a second output terminal, and a decoder may be provided. The decoder is configured to receive first control bits, generate second control bits from the first control bits, generate third and fourth control bits from the first or second control bits, respectively, transmit the first control bits and the third control bits to the third and fourth variable resistors to adjust resistance values, and transmit the second and fourth control bits to first and second variable resistors to adjust resistance values.

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 bidirectional amplifier includes first and second ports, with a first summing node connected to the first port and a second summing node connected to the second port. First and second gain stages are connected between the first and second summing nodes, respectively, and a first node. First and second feedback stages are also connected between the first and second summing nodes, respectively, and the first node. The amplifier operates in a first mode in which an amplified version of a signal applied to the first port is provided at the second port, or a second mode in which an amplified version of a signal applied to the second port is provided at the first port. The first and second gain stages are preferably first and second common emitter cascode arrangements, and the first and second feedback stages are preferably first and second emitter followers.

An electronic circuit includes: a variable amplitude control circuit that controls an amplitude of a first radio-frequency signal being a single-ended signal in accordance with a control signal that continuously changes and that outputs a second radio-frequency signal being a single-ended signal; and a balun that converts the second radio-frequency signal into differential signals and outputs a pair of third radio-frequency signals.

A method of increasing a current flowing through an inductor includes receiving an input signal with a driver stage, the driver stage including the inductor coupled in series with a loading between an output node of the driver stage and a power line. In response to a transition in the input signal from a first voltage state to a second voltage state, a first current flowing through the loading and the inductor is increased. During the transition in the input signal, the current flowing through the inductor is increased by increasing a second current in a circuitry though a node between the inductor and the loading.

A system has a baseband gain stage to receive incoming in-phase and quadrature voltage signals and output in-phase and quadrature current signals, a mixer core arranged to receive the in-phase and quadrature current signals and output radio frequency signals, and a variable gain amplifier to receive the radio frequency signals and produce a broadband radio signal.

A variable gain amplifying circuit incorporates an operational amplifier, an input device, a feedback device, a transconductance circuit, and a dynamic biasing circuit. The operational amplifier has an output terminal providing an amplified difference output signal. The input device has a first terminal receiving a first input signal, and a second terminal coupled to a first input terminal of the operational amplifier. The feedback device is coupled between the first input terminal of the operational amplifier and the output terminal of the operational amplifier. The dynamic biasing circuit generates a bias current according to a set value. The transconductance circuit converts the difference between the first input signal and a second input signal into an analog output current flowing through the feedback device. The analog output current of the transconductance circuit is varied according to the bias current.

In high speed communication applications, e.g., optical communication, a variable gain amplifier is used for input signal amplitude normalization or for linear equalization. Traditionally a bipolar Gilbert multiplier circuit is used. When moving towards a low-power application, a modified circuit topology is implemented to reduce the minimum supply voltage requirement of the variable gain amplifier while ensuring that bias current levels remain substantially the same and achieving the same current switching capacity as the traditional circuit. As a result, the power consumption of the circuit can be greatly reduced. The modified circuit topology combines the amplifier and gain transistors and achieves gain programming using a voltage difference of two pairs of floating voltage sources.