Psemi Corporation

Khushali Shah

Rong Jiang

Parvez Daruwalla

Peter Bacon

Haopei Deng

Yucheng Tong

Sung Kyu Han

Ping Wing Lai

Ravindranath D Shrivastava

Feedback methods and devices to reduce gain in RF amplifiers, more in particular LNAs, are disclosed. The described methods are based on providing feedback paths from the drain terminal of one of the LNA cascode transistors to the source terminal of the LNA input transistor, or from the gate terminal of the input transistor to the source terminal of the LNA input transistor. The disclosed methods can be combined with one another or with existing feedback methods to provide further flexibility and improved tradeoffs when designing LNAs for applications having different requirements.

Feedback topologies for amplifier gain reduction

Circuits and methods for generating a bypass pulse to an RF circuit that increases the response time of the circuit to mode changes. Embodiments include a pulse generation circuit that it is self-initiated and self-terminated, generating a bypass pulse as a function of voltages Vand Valong a signal path. Voltage V, a scaled version of V, is compared to a voltage Vderived from Vand a pulse is output while V>V. The pulse temporarily lowers the signal path impedance, reducing the RC time constant of the signal path and allowing fast charging of components coupled to the signal path. The pulse may be used with any other circuit that needs a faster settling time after a mode change but is slowed down by an RC time constant. Usage also extends to providing for rapid discharge of the signal path by adding additional logic components.

Dynamic fast charge pulse generator for an RF circuit

Methods and devices to support multiple frequency bands in radio frequency (RF) circuits are shown. The described methods and devices are based on adjusting the effective width of a transistor in such circuits by selectively disposing matching transistors in parallel with the transistor. The presented devices and methods can be used in RF circuits including low noise amplifiers (LNAs), RF receiver front-ends or any other RF circuits where input matching to wideband inputs is required.

Supporting wideband inputs on RF receivers

Methods and devices to implement efficiently an AUX terminal in RF front end receivers using LNAs are described. The described methods implement a smaller number of switches resulting in an overall performance improvement by reducing the noise figure at the input of the LNA. The presented devices can be used in low/high gain and bypass modes and can accommodate an arbitrary number of bands over a wide frequency range.

Wideband auxiliary input for low noise amplifiers

A clamping circuit that may be used to provide efficient and effective voltage clamping in an RF front end. The clamping circuit comprises two series coupled signal path switches and a bypass switch coupled in parallel with the series coupled signal path switches. A diode is coupled from a point between the series coupled signal path switches to a reference potential. In addition, an output selection switch within an RF front end has integrated voltage clamping to more effectively clamp the output voltage from the RF front end. Additional output clamping circuits can be used at various places along a direct gain signal path, along an attenuated gain path and along a bypass path.

Method and apparatus to optimize power clamping

Compact low noise amplifiers that have wide-band coverage while meeting necessary input matching and output matching characteristics. Embodiments include a wide-band, two-stage LNA with minimum degradation in performance compared to multiple narrow-band, single-stage LNAs. A generalized embodiment includes a first amplifier stage having a terminal coupled to a mutually coupled inductor circuit and to a second amplifier stage. The second amplifier stage includes a terminal coupled to the mutually coupled inductor circuit. The mutually coupled inductor circuit comprises electromagnetically coupled inductors L, L. Second terminals of the first and second amplifier stages are coupled to respective degeneration inductors. The electromagnetically coupled inductors L, Lof the inductor circuit substantially increase the output bandwidth of the LNA with minimum degradation in performance.

Two-stage LNA with mutual coupling

Methods and devices to support multiple gain states in amplifiers are described. The methods and devices are based on implementing a feedback element in the amplifier and adjusting the impedance of the feedback element to provide a desired gain while maintaining the overall performance of the amplifier and reducing degradation of the S12 parameter. The feedback element includes an adjustable attenuator and a tunable resistive element. The adjustable attenuator is provided in a path that is common to the feedback path and the bypass path of the amplifier. Exemplary implementations of adjustable attenuators are also presented.

Amplifiers with attenuator in feedback and bypass paths

Programmable clamping methods and devices providing adjustable clamping powers to accommodate different applications and requirements are disclosed. The described devices can use switchable clamping circuits having different structures, body-controlled clamping circuits, or clamping circuits adjusting their input power levels using programmable resistive ladders. Examples of how the disclosed devices can be combined to improve design flexibility are also provided.

Programmable clamping devices and methods

Circuits and methods for generating a bypass pulse to an RF circuit that increases the response time of the circuit to mode changes. Embodiments include a pulse generation circuit that it is self-initiated and self-terminated, generating a bypass pulse as a function of voltages Vand Valong a signal path. Voltage V, a scaled version of V, is compared to a voltage Vderived from Vand a pulse is output while V&#x3e;V. The pulse temporarily lowers the signal path impedance, reducing the RC time constant of the signal path and allowing fast charging of components coupled to the signal path. The pulse may be used with any other circuit that needs a faster settling time after a mode change but is slowed down by an RC time constant. Usage also extends to providing for rapid discharge of the signal path by adding additional logic components.

Circuits and methods for improving the noise figure (NF) of an amplifier, particularly an LNA, in high-gain modes while improving the IIP3 of the amplifier in low-gain modes. The source of an amplifier common-source FET is coupled to circuit ground thorough a degeneration circuit comprising a two-port inductor and a bypass switch coupled in parallel with the inductor. A switched feedback circuit is coupled between the gate of the common-source FET and a feedback node in the amplifier output signal path. During a low gain mode, the inductor is entirely bypassed and the enabled feedback circuit lowers the input impedance of the common-source FET and reduces the gain of the amplifier circuit, essentially eliminating the need for a degeneration inductor. During a high gain mode, the source of the common-source FET is coupled to circuit ground through the inductor and the feedback circuit is disabled. Other gain modes are supported.

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San Diego, CA, United States of America

Khushali Shah