A single-stage radio frequency amplifier is provided with a signal amplification stage for a magnetic resonance tomography scanner, for example as a low-noise preamplifier in a local coil. The radio frequency amplifier includes a signal input, a signal amplifier, a signal output of the signal amplifier and a phase shifter. The phase shifter is in signal connection with the signal output and the signal input of the signal amplifier and is configured to couple a predetermined portion of an output signal of the signal amplifier with a predetermined phase shift into the signal input of the signal amplifier.

A buffer circuit is provided. The buffer circuit includes a Current Differencing Transconductance Amplifier (CDTA) comprising a first input node and a second input node each configured to receive a respective one of a first signal and a second signal. The buffer circuit further includes a first source follower circuit coupled to a first output node of the CDTA and configured to generate a first buffer output signal based on a first output signal of the CDTA. Additionally, the buffer circuit includes a second source follower circuit coupled to a second output node of the CDTA and configured to generate a second buffer output signal based on a second output signal of the CDTA. The buffer circuit further includes a first feedback path comprising at least one of a first resistive element and a first capacitive element. The first feedback path couples an output node of the first source follower circuit to the first input node of the CDTA. In addition, the buffer circuit includes a second feedback path comprising at least one of a second resistive element and a second capacitive element. The second feedback path couples an output node of the second source follower circuit to the second input node of the CDTA.

A voltage supply circuit includes a rectifier circuit, a charging circuit, a feedback circuit and an energy storage circuit. The rectifier circuit is used to receive an input voltage to generate a rectified energy. The charging circuit is coupled to the rectifier circuit and has a modulation input terminal and an energy supply terminal. The modulation input terminal is used to receive a modulation voltage, and the energy supply terminal is used to selectively output a charging current according to the modulation voltage. The feedback circuit is used to receive a high voltage signal and a supply voltage, and output the modulation voltage to the modulation input terminal. The feedback circuit is used to adjust the modulation voltage according to a difference between the supply voltage and a reference voltage. The energy storage circuit is charged by the charging current to pull up the supply voltage.

This application relates to circuitry for monitoring for instability of an amplifier. The amplifier (100) has a first signal path between an amplifier input (IN.sub.N) and an amplifier output (V.sub.OUT) and a feedback path from the output to form a feedback loop with at least part of the first signal path. A comparator (212) has a first input configured to receive a first signal (IN.sub.N) derived from a first amplifier node which is part of said feedback loop and a second input configured to receive a second signal (IN.sub.P) derived from a second amplifier node which varies with the signal at the amplifier input but does not form part of said feedback loop. The comparator is configured to compare the first signal to the second signal and generate a comparison signal (COMP), wherein in the event of amplifier instability the comparison signal comprises a characteristic indicative of amplifier instability.

The present disclosure discloses a thin film transistor (TFT)-based bootstrap structure amplifier, and a chip. The amplifier includes an input circuit, an output buffer, and several bootstrap structure units. The bootstrap structure units include a TFT and a capacitor. The drain and the gate of the TFT are both connected to the same voltage node. The source of the TFT is connected to one end of the capacitor. The other end of the capacitor is connected to an output signal node. The output buffer is formed by connecting the sources and drains of several TFTs in series. Two ends of the output buffer are respectively connected to an input voltage node and an output signal node. The source of the TFT in each bootstrap structure unit is connected to the gates of the TFTs in one output buffer. The input circuit includes an input signal node, the output signal node, and a grounding node. The present disclosure can increase circuit gain and have a simple structure and low fabrication cost. The present disclosure can be widely applied to the field of integrated circuits.

The use of a capacitor (22) to serve as the principal impedance in a negative feed-back loop in a voltage amplifier component (21) of a trans-impedance amplifier and actively controlling the amount of charge accumulated within the capacitor appropriately to improve the responsiveness and/or dynamic range of the amplifier. A switch (25) is electrically coupled to the inverting input terminal of the voltage amplifier and electrically isolated from the output terminal (23) of the voltage amplifier. The output voltage of the amplifier is proportional to the accumulation of charge, and the switch is operable to ‘reset’ the charge/voltage on the feedback capacitor, as desired. This arrangement decouples the structure of the switch from the output port of the voltage amplifier, and so avoids leakage currents and/or interfering voltage signals emanating from the switch structure and being felt at the output port of the voltage amplifier.

The use of a capacitor (22) to serve as the principal impedance in a negative feed-back loop in a voltage amplifier component (21) of a trans-impedance amplifier and actively controlling the amount of charge accumulated within the capacitor appropriately to improve the responsiveness and/or dynamic range of the amplifier. A switch (25) is electrically coupled to the inverting input terminal of the voltage amplifier and electrically isolated from the output terminal (23) of the voltage amplifier. The output voltage of the amplifier is proportional to the accumulation of charge, and the switch is operable to ‘reset’ the charge/voltage on the feedback capacitor, as desired. This arrangement decouples the structure of the switch from the output port of the voltage amplifier, and so avoids leakage currents and/or interfering voltage signals emanating from the switch structure and being felt at the output port of the voltage amplifier.

The present invention provides a differential to single-ended converter including a first input node, a second input node, an operational amplifier and a feedback circuit. The operational amplifier has a first terminal and a second terminal, wherein the first terminal of the operational amplifier receives a first signal from the first input terminal, and the second terminal of the operational amplifier receives a second signal from the second input terminal. The feedback circuit is configured to receive an output signal of the operational amplifier and generate a first feedback signal to the first terminal of the operational amplifier to reduce a swing of the first signal, and generate a second feedback signal to the second terminal of the operational amplifier to balance noises induced by the feedback circuit and inputted to the first terminal and the second terminal.

This invention relates to a self-excited oscillation suppression device and method for the power amplifying circuit, belonging to the field of electronic technology. Said power amplifying circuit includes a FET and a feedback loop. Said device includes: a first compensation circuit which is connected between a drain and a gate of the FET and a second compensation circuit which is connected in parallel with a feedback resistor of said feedback loop. It can solve self-excited oscillation caused by deep negative feedback in the existing power amplifying circuit. The first compensation circuit can shift the open-loop gain curve forward as a whole, and the second compensation circuit can speed up the closure of the feedback gain curve and the open-loop gain curve so that the two curves will close up before the self-excited oscillation; the self-excited oscillation will be suppressed, and the stability of the power amplifying circuit will be improved.

According to an embodiment of the disclosure, a series or source feedback is provided to a solid-state power amplifier to achieve improved amplifier output power, good impedance match, and low voltage standing wave ratio (VSWR). In an embodiment, an inductive element is coupled to the source of the power amplifier transistor to serve as a series or source feedback for the transistor. In an embodiment, a high-impedance transmission line such as a microstrip or coplanar waveguide is provided as an inductive element coupled to the source of the transistor. In an embodiment, a series or source feedback is provided to each amplifier in a multistage amplifier circuit.