An amplifier circuit includes an amplifier having an amplifier input and an amplifier output. A transformer disposed to provide a signal for driving a load includes a primary winding in series with the amplifier output. A secondary winding of the transformer is coupled to the amplifier input where the primary winding and the secondary winding are arranged such that a portion of a magnetic field generated by the primary winding couples to the secondary winding so as to establish a magnetically coupled feedback loop from the amplifier output to the amplifier input. A loop gain of the magnetically coupled feedback loop is substantially independent of an impedance of the load and is defined at least in part by a coupling factor and turn-ratio of the transformer. The load may be included within an output load arrangement including a balun.

An amplifier includes an input node, an output node, a transistor and a transformer. The input node is configured to receive a first signal. The output node is configured to output an amplified first signal. The transistor includes a first terminal, a second terminal and a third terminal. The first terminal is coupled to the input node and a first supply voltage source. The second terminal is coupled to a second supply voltage source and the output node. The third terminal is coupled to a reference node. The transformer is coupled to the first terminal and the third terminal. The transistor is configured to operate in a sub-threshold region and a near-triode region.

Amplifiers can be used for a variety of electronic-based applications. Therefore, amplifier performance is of importance. A low noise amplifier can be interfaced after an antenna or a band-select filter as a first active stage, in a receiver since its bandwidth characteristics can be closely related to a system data rate. A bandwidth enhancement technique can be leverage for low noise amplifiers by embedding a transformer between a gate and a drain terminal of a common gate transistor in a cascode topology. The embedded transformer can introduce an additional high-frequency conjugate zero pair, which can push the gain rolling-off start-up point to a higher frequency, peak the higher frequency gain, and broaden the low noise amplifier gain bandwidth.

An amplifier circuit includes an amplifier having an amplifier input and an amplifier output. The amplifier circuit includes a transformer having a primary winding in series with the amplifier output and a secondary winding coupled to the amplifier input. The primary winding and the secondary winding are arranged such that a portion of a magnetic field generated by the primary winding couples to the secondary winding through a magnetically coupled feedback loop, thereby providing feedback from the amplifier output to the amplifier input. An output load arrangement is connected to the primary winding wherein the output arrangement includes a balun. The amplifier circuit may be implemented as an integrated circuit and where the primary and secondary windings are integrated in different metal layers of the integrated circuit or are otherwise arranged to effect a desired degree of magnetic coupling and feedback from the amplifier output to the amplifier input.

Aspects of this disclosure relate to an impedance transformation circuit and overload protection for a low noise amplifier. A low noise amplifier can include a first inductor, an amplification circuit configured to amplify a radio frequency signal, and a second inductor magnetically coupled to the first inductor to provide negative feedback to linearize the low noise amplifier. A switch can be coupled to the amplification circuit of the low noise amplifier. An overload protection circuit can adjust an impedance of the switch based on a signal level associated with the radio frequency signal to provide overload protection for the low noise amplifier.

Techniques for providing low-cost and effective jammer rejection for an amplifier is disclosed. The amplifier includes an input node and an output node, a first transistor and a second transistor, a load circuitry, an inductor, and a capacitor. A first terminal of the first transistor is coupled to a ground. A second terminal of the first transistor is coupled to a first terminal of the second transistor. A second terminal of the second transistor is coupled to the output node. The load circuitry is coupled between a power supply and the second terminal of the second transistor. A first terminal of the inductor is coupled to the ground through a first switch. A first terminal of the capacitor is coupled to the first terminal of the second transistor and a second terminal of the capacitor is coupled to a second terminal of the inductor.

A low-power standard-compliant NB-IoT wake-up receiver (WRX) is presented. The WRX is designed as a companion radio to a full NB-IoT receiver, only operating during discontinuous RX modes (DRX and eDRX), which allows the full high-power radio to turn off while the wake-up receiver efficiently receives NB-IoT Wake-Up Signals (WUS). The fabricated receiver achieves 2.1 mW power at 109 dBm sensitivity with 180 KHz bandwidth over the 750-960 MHz bands. The WRX is fabricated in 28 nm CMOS and consumes 5 less power than the best previously published traditional NB-IoT receivers. This disclosure is the first designed dedicated wake-up receiver for the NB-IoT protocol and demonstrates the benefits of utilizing a WRX to reduce power consumption of NB-IoT radios.

A low noise amplifier includes an amplifier transistor having a source, a gate, and a drain. An input node is coupled to the gate. An output node is coupled to the drain. An inductor is coupled between the gate and the drain.

Aspects of this disclosure relate to an impedance transformation circuit for use in an amplifier, such as a low noise amplifier. The impedance transformation circuit includes a matching circuit including a first inductor. The impedance transformation circuit also includes a second inductor. The first and second inductors are magnetically coupled to each other to provide negative feedback to linearize the amplifier.

A radio frequency low noise amplifier circuit with a receive signal input, a receive signal output, and a voltage source include a low noise amplifier and a coupled inductor circuit with a primary inductive chain connected to the output of the low noise amplifier and to the voltage source. The coupled inductor circuit further includes a secondary inductive chain with a first inductor electromagnetically coupled to the primary inductive chain, and a second inductor in series with the first inductor and magnetically coupled to the primary inductive chain. The second inductor is connected to a feedback node of the low noise amplifier. There is an output matching network connected to the first inductor of the secondary inductive chain and to the receive signal output.