Amplifier circuits, radio communication circuits, radio communication devices, and methods provided in this disclosure. The amplifier circuit may include an amplifier configured to amplify an input signal to provide an output signal. The output signal of the amplifier may include a direct current (DC) signal. The amplifier circuit may further include a current source coupled to the amplifier. The current source may be configured to receive an electrical supply. The current source may further be configured to divide the direct current (DC) signal of the output signal based on the electrical supply.

In a semiconductor device according to an embodiment, a thickness of a semiconductor layer of an SOI substrate on which a field effect transistor constituting an analog circuit is formed is set to 2 nm or more and 24 nm or less.

Methods, systems, and devices for delay adjustment circuits are described. Amplifiers (e.g., differential amplifiers) may act like variable capacitors (e.g., due to the Miller-effect) to control delays of signals between buffer (e.g., re-driver) stages. The gains of the amplifiers may be adjusted by adjusting the currents through the amplifiers, which may change the apparent capacitances seen by the signal line (due to the Miller-effect). The capacitance of each amplifier may be the intrinsic capacitance of input transistors that make up the amplifier, or may be a discrete capacitor. In some examples, two differential stages may be inserted on a four-phase clocking system (e.g., one on 0 and 180 phases, the other on 90 and 270 phases), and may be controlled differentially to control phase-to-phase delay.

Amplifiers, amplification circuits, and phase shifters, for example, for flexibly adjusting an output phase to thereby meet a requirement of a constant phase on a link in a communications field, are provided. In one aspect, an amplifier includes first, second, and third MOS transistors. The first MOS transistor includes a gate separately coupled to a signal input end and a bias voltage input end, a source coupled to a power supply, and a drain separately coupled to sources of the second and third MOS transistors. A drain of the third MOS transistor is coupled to a ground, and a drain of the second MOS transistor is coupled to a signal output end. The bias voltage input end is configured to receive a bias voltage to adjust a phase difference between an input signal at the signal input end and an output signal at the signal output end.

An output gain of a latch circuit is increased. The latch circuit includes a first circuit, a second circuit, and first to fourth transistors. The latch circuit includes a first input/output terminal and a second input/output terminal. The first circuit and the second circuit have a function of a current source. In the case where the third transistor is off and the fourth transistor is on, the latch circuit is supplied with a first input signal supplied to the first input/output terminal and a second input signal supplied to the second input/output terminal. In the case where the third transistor is on and the fourth transistor is off, an inverted signal of the first input signal is output to the first input/output terminal of the latch circuit, and an inverted signal of the second input signal is output to the second input/output terminal of the latch circuit. The first circuit and the second circuit increase the output gain of the latch circuit.

A variable gain amplifier includes a first transconductor circuit coupled to a first input terminal, a first output terminal, and a second output terminal of the variable gain amplifier, the first transconductor circuit including: a plurality of positive coefficient transistors coupled to the first output terminal and configured to selectively conduct current in response to a first binary code, a plurality of negative coefficient transistors coupled to the second output terminal and configured to selectively conduct current in response to a second binary code, and a plurality of amplifying transistors, each having a gate electrode coupled to the first input terminal, a first electrode coupled to a ground reference, and a second electrode coupled to a pair of coefficient transistors including one of the plurality of positive coefficient transistors and one of the plurality of negative coefficient transistors.

An operational amplifier 1 comprises transistors Q1 and Q2 forming an input stage, and input resistors R1 and R2 which form a filter together with parasitic capacitors C1 and C2 accompanying the transistors Q1 and Q2. Resistance values R of the resistors R1 and R2 may be set to R=1/(2π.Math.fc.Math.C), where C is the capacitance value of each of the parasitic capacitors C1 and C2, and fc is the target cutoff frequency of the filter. The operational amplifier 1 may also include a power supply resistor R0 which forms a filter together with a parasitic capacitor C0 accompanying a power supply line.

An apparatus for turning off a cascode amplifier having a common-base transistor and a common-emitter transistor is disclosed that includes the cascode amplifier, a feedback circuit, and a bias circuit. The feedback circuit is configured to receive a collector-voltage from the collector of the common-emitter transistor when the common-emitter transistor is switched to a first OFF state and produce a first feedback signal. The collector-voltage is equal to an emitter voltage of the common-base transistor and the collector-voltage increases in response to switching the common-emitter transistor to the first OFF state. The bias circuit is configured to receive the first feedback signal and produce a bias-voltage. A first base-voltage is produced from the bias-voltage. The cascode amplifier is configured to receive the first base-voltage and a second base-voltage. The common-base transistor is configured to switch to a second OFF state in response to receiving the second base-voltage.

A circuit is disclosed, in accordance with some embodiments. The circuit includes a transistor stage, a resistive element, a first tunable capacitive element and a second tunable capacitive element. The transistor stage includes a first input/output terminal and a second input/output terminal. The resistive element is connected to the transistor stage. The first tunable capacitive element is connected in parallel with the resistive element. The second tunable capacitive element is connected to the second input/output terminal of the transistor stage.

An optical receiver disclosed includes a bias terminal, an input terminal, a photodiode, an amplifier circuit, a first resistor, a bypass circuit, a filter circuit, and a control circuit. The photodiode receives a bias from the filter circuit through the bias terminal, and outputs a current signal to the amplifier circuit through the input terminal. The amplifier circuit converts an input current to an output voltage. The bypass circuit electrically connected to the input terminal decreases a first input impedance viewed from the input terminal, when activated, and increases the first input impedance, when deactivated. The filter circuit increases a second input impedance viewed from the bias terminal, when a dumping function thereof is activated, and decreases the second input impedance, when the dumping function is deactivated. The control circuit activates the dumping function and the bypass circuit, when the output voltage is larger than a certain voltage.