Abstract: A circuit includes a Doherty power amplifier circuit configured to amplify an input signal and generate an amplified signal of the input signal. The Doherty power amplifier circuit includes a first power amplifier circuit configured to operate in class C. The circuit further includes a bias circuit electrically coupled to the first power amplifier circuit. The bias circuit is configured to generate a bias based on the input signal, and to bias the first power amplifier circuit using the generated bias.

Abstract: A low-loss Radio Frequency (RF) switch for high-power RF signals. The RF switch includes a first-biasing circuit connected to a first transistor and a second-biasing circuit connected to a second transistor. The RF switch switches its output signal between a first input signal and a second input signal. The first transistor is in a conduction state and the second transistor is in a non-conduction state when the first input signal is to be conducted to the output signal. The first-biasing circuit biases the first transistor at a first voltage for increasing conduction of the first input signal and the second-biasing circuit biases the second transistor at a second voltage for decreasing conduction of the first input signal. Moreover, the second transistor is in a conduction state and the first transistor is in a non-conduction state when the second input signal is to be conducted to the output signal.

Abstract: A low-loss Radio Frequency (RF) switch for high-power RF signals. The RF switch includes a first-biasing circuit connected to a first transistor and a second-biasing circuit connected to a second transistor. The RF switch switches its output signal between a first input signal and a second input signal. The first transistor is in a conduction state and the second transistor is in a non-conduction state when the first input signal is to be conducted to the output signal. The first-biasing circuit biases the first transistor at a first voltage for increasing conduction of the first input signal and the second-biasing circuit biases the second transistor at a second voltage for decreasing conduction of the first input signal. Moreover, the second transistor is in a conduction state and the first transistor is in a non-conduction state when the second input signal is to be conducted to the output signal.

Abstract: A variable gain amplifier is disclosed where the gain of the amplifier is controlled by a variable emitter resistor that is responsive to a control signal. The variable resistor includes a resistor connected between the collector and emitter of a control transistor. A control signal applied to the base of the control transistor varies the gain of the amplifier from a minimum gain when the control transistor is cut-off to a maximum gain when the control transistor is saturated.

Abstract: A transistor bias circuit is provided that is capable of operating from a power supply voltage that is slightly higher than twice the base-emitter voltage of the transistor to be biased. The bias circuit includes a transistor connected in a current-mirror configuration with the transistor to be biased. A feedback circuit maintains the mirrored current at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. In a preferred embodiment, the biased transistor is concurrently in both a Darlington and the current mirror configuration. Moreover, a feedback transistor in the feedback circuit is also concurrently in the Darlington configuration, thus providing an efficient biasing arrangement for an amplifier block based on the Darlington arrangement.

Abstract: There is disclosed a bias circuit exhibiting good stability over variations in temperature and power supply voltage and capable of generating a plurality of discrete levels of output current for biasing RF power amplifier. In accordance with the invention, the bias circuit includes (1) a master transistor connected to the slave transistor in a current-mirror configuration and having two parallel-connected transistor elements, (2) a switch connected to at least one transistor element to control its operation, and (3) a feedback circuit by which the voltage at the collector of the master transistor may be fed back to control the voltages at the bases of the master transistor and the slave transistor. Moreover, the bias circuit can be operated from a power supply voltage that is just above twice the value of the base-emitter voltage of the transistor in the circuit.

Abstract: A transistor bias circuit is provided that is capable of operating from a power supply voltage that is slightly higher than twice the base-emitter voltage of the transistor to be biased. The bias circuit includes a transistor connected in a current-mirror configuration with the transistor to be biased. A feedback circuit maintains the mirrored current at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. In a preferred embodiment, the biased transistor is concurrently in both a Darlington and the current mirror configuration. Moreover, a feedback transistor in the feedback circuit is also concurrently in the Darlington configuration, thus providing an efficient biasing arrangement for an amplifier block based on the Darlington arrangement.

Abstract: There is disclosed a bias circuit exhibiting good stability over variations in temperature and power supply voltage and capable of generating a plurality of discrete levels of output current for biasing RF power amplifier. In accordance with the invention, the bias circuit includes (1) a master transistor connected to the slave transistor in a current-mirror configuration and having two parallel-connected transistor elements, (2) a switch connected to at least one transistor element to control its operation, and (3) a feedback circuit by which the voltage at the collector of the master transistor may be fed back to control the voltages at the bases of the master transistor and the slave transistor. Moreover, the bias circuit can be operated from a power supply voltage that is just above twice the value of the base-emitter voltage of the transistor in the circuit.

Abstract: A transistor bias circuit is provided that is capable of operating from a power supply voltage that is slightly higher than twice the base-emitter voltage of the transistor to be biased. The bias circuit includes a transistor connected in a current-mirror configuration with the transistor to be biased. A feedback circuit maintains die mirrored current at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit.

Abstract: A transistor bias circuit is provided that is capable of operating from a power supply voltage that is slightly higher than twice the base-emitter voltage of the transistor to be biased. The bias circuit includes a transistor connected in a current-mirror configuration with the transistor to be biased. A feedback circuit maintains the mirrored current at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit.

Abstract: Internal to the transistor, an additional, direct connection is made from the internal collector to the external collector of the transistor by a fixed shunt inductance. The external power supply V.sub.s is applied to the transistor collector through an adjustable external shunt element. The adjustable external shunt element allows the user to finetune the impedance matching circuit such that the transformation ratio of the output matching circuitry is minimized.