A transistor circuit includes a transistor having a gate terminal and first and second conduction terminals, a first circuit configured to convert an AC input signal of the transistor circuit to a gate bias voltage and to apply the gate bias voltage to the gate terminal of the transistor, a second circuit configured to convert the AC input signal of the transistor circuit to a control voltage, and a switching circuit configured to apply a first voltage to the first conduction terminal of the transistor in response to the control voltage.

An apparatus is disclosed for complementary variable gain amplification. In an example aspect, the apparatus includes a variable gain amplifier that includes multiple amplifiers. The multiple amplifiers include at least one first amplifier and at least one second amplifier cascaded together in series. The first amplifier includes a first set of transistors having a first doping type. At least a portion of the first set of transistors is configured to implement a first current mirror. The second amplifier includes a second set of transistors having a second doping type. At least a portion of the second set of transistors is configured to implement a second current mirror. The second current mirror is coupled to the first current mirror.

A receiver front end capable of receiving and processing intraband non-contiguous carrier aggregate (CA) signals using multiple low noise amplifiers (LNAs) is disclosed herein. A cascode having a common source configured input FET and a common gate configured output FET can be turned on or off using the gate of the output FET. A first switch is provided that allows a connection to be either established or broken between the source terminal of the input FET of each LNA. Further switches used for switching degeneration inductors, gate capacitors and gate to ground caps for each legs can be used to further improve the matching performance of the invention.

An amplifier includes a semiconductor substrate. A first conductive feature partially covers the bottom substrate surface to define a conductor-less region of the bottom substrate surface. A first current conducting terminal of a transistor is electrically coupled to the first conductive feature. Second and third conductive features may be coupled to other regions of the bottom substrate surface. A first filter circuit includes an inductor formed over a portion of the top substrate surface that is directly opposite the conductor-less region. The first filter circuit may be electrically coupled between a second current conducting terminal of the transistor and the second conductive feature. A second filter circuit may be electrically coupled between a control terminal of the transistor and the third conductive feature. Conductive leads may be coupled to the second and third conductive features, or the second and third conductive features may be coupled to a printed circuit board.

A system for testing a subject transistor with constant power. The system may include an amplifier, a measurement voltage source, and a exercise voltage source. The amplifier may have an output connected to a gate of the subject transistor. The amplifier may have a first input and a second input. The measurement voltage source may be connected to the first input of the amplifier for use in measuring characteristics of the subject transistor. The exercise voltage source may be connected to the first input of the amplifier for exercising the subject transistor. The second input of the amplifier may be connected to a source of the subject transistor through a resistor.

A preamplifier circuit includes a first transconductor and a floating transconductor. The first transconductor receives a differential voltage from a sample-and-hold circuit and drives the floating transconductor. The first and floating transconductors output amplified versions of the differential voltage that are not affected by capacitive division, which makes the preamplifier circuit fast. The preamplifier circuit also has a low input capacitance because the floating transconductor is not connected to any external circuitry.

A capacitive load driving circuit includes a first switching element, a second switching element, a third switching element, a fourth switching element and voltage dropper elements. The first switching element is provided on a first charging path extending from a power supply to a capacitive load. The second switching element is provided on a second charging path extending from a capacitor to the capacitive load. The third switching element is provided on a first discharging path extending from the capacitive load to a ground. The fourth switching element is provided on a second discharging path extending from the capacitive load to the capacitor. The voltage dropper elements are provided on each of control signal power supply paths to the first switching element, to the second switching element, to the third switching element and to the fourth switching element. The voltage dropper elements are configured to make electric current flow more easily through the second charging path than through the first charging path when charging the capacitive load and to make electric current flow more easily through the second discharging path than through the first discharging path when discharging the capacitive load by a potential difference.

Methods and devices used in mobile receiver front end to support multiple paths and multiple frequency bands are described. The presented devices and methods provide benefits of scalability, frequency band agility, as well as size reduction by using one low noise amplifier per simultaneous outputs. Based on the disclosed teachings, variable gain amplification of multiband signals is also presented.

A control circuit with a bypass function includes a first signal terminal, a second signal terminal, an output terminal, a first switch unit to a fourth switch unit, an output switch unit and a bypass unit. The first signal terminal is used for receiving a first signal. The second signal terminal is used for receiving a second signal. The first switch unit is coupled to the first signal terminal. The second switch unit is coupled between the first switch unit and the output switch unit. The third switch unit is coupled to the second signal terminal. The fourth switch unit is coupled between the third switch unit and the output switch unit. The output switch unit is coupled between the second switch unit and the output terminal. The bypass unit is coupled between the first switch unit and the output terminal to provide a bypass path corresponding to the first signal.

An apparatus is disclosed for complementary variable gain amplification. In an example aspect, the apparatus includes a variable gain amplifier that includes multiple amplifiers. The multiple amplifiers include at least one first amplifier and at least one second amplifier cascaded together in series. The first amplifier includes a first set of transistors having a first doping type. At least a portion of the first set of transistors is configured to implement a first current mirror. The second amplifier includes a second set of transistors having a second doping type. At least a portion of the second set of transistors is configured to implement a second current mirror. The second current mirror is coupled to the first current mirror.