Abstract: An RF power amplifier operates over the range of supply voltages provided by a DC/DC converter whether the range of voltages is intentional or unintentional. A system for digitally adjusting the bias levels relative to the supply voltage includes at least one RF power amplifier stage, a digital control block, and a bias circuit. The RF power amplifier stage has at least one RF input signal, at least one RF output signal, and at least one bias input that controls its bias conditions. The RF Power Amplifier Stage includes one or more active gain elements used to amplify the RF input signals. The RF power amplifier operates in a number of bias states controlled by the digital control block. The digital control block uses information related to the supply voltage and may use other information stored in memory to select the desired bias.

Abstract: A radio frequency (RF) power amplifier (PA) is reconfigured to operate in a low power mode from a high power mode. The RF PA has a first RF amplifier is connected to the first and second inputs of a first transformation network. The RF PA has a second a second RF amplifier connected to a second transformation network. During high power mode, both RF amplifiers drive a load coupled to the transformation networks. In low power mode the first RF amplifier is disabled and the first and second inputs of the first transformation are coupled together so as to change the load impedance seen by the second RF amplifier. The second RF amplifier continues to supply power to the load during operation in the low power mode.

Abstract: One embodiment of a power supply apparatus includes a first switcher coupled to provide VOUT from a VSUPPLY. A cascaded second switcher is coupled to provide a subscriber line interface circuit target VBAT from VOUT, wherein the first switcher is placed in one of an active mode and an inactive mode in accordance with a function of VSUPPLY and VBAT, wherein in the active mode ? VOUT VSUPPLY ? ? 1 , wherein in the inactive mode VOUT?VSUPPLY.

Abstract: A radio frequency (RF) power amplifier includes a low impedance pre-driver driving the input of a common-source output amplifier stage. The preamplifier includes a first transistor that has a first terminal coupled to a preamplifier RF input node, a second terminal coupled to a preamplifier RF output node, and a third terminal coupled to a supply voltage node. A first inductor is coupled between the RF output node and a bias voltage node. A voltage difference between respective first and second voltages on the RF input node and the RF output node that are substantially in phase, determines current through the first transistor.

Abstract: A radio frequency (RF) power amplifier includes a low impedance pre-driver driving the input of a common-source output amplifier stage. The preamplifier includes a first transistor that has a first terminal coupled to a preamplifier RF input node, a second terminal coupled to a preamplifier RF output node, and a third terminal coupled to a supply voltage node. A first inductor is coupled between the RF output node and a bias voltage node. A voltage difference between respective first and second voltages on the RF input node and the RF output node that are substantially in phase, determines current through the first transistor.

Abstract: In one embodiment, a subscriber line interface circuit includes circuitry to generate metering pulses for insertion onto a subscriber line. The circuitry includes an audio path and a pulse metering path, where the pulse metering path includes a metering generator to generate a digital sine wave from a plurality of stored values, a first interpolator to interpolate the digital sine wave, a filter to filter the interpolated digital sine wave, and a second interpolator to interpolate the filtered interpolated digital sine wave.

Abstract: A radio frequency (RF) power amplifier includes a low impedance pre-driver driving the input of a common-source output amplifier stage. The preamplifier includes a first transistor that has a first terminal coupled to a preamplifier RF input node, a second terminal coupled to a preamplifier RF output node, and a third terminal coupled to a supply voltage node. A first inductor is coupled between the RF output node and a bias voltage node. A voltage difference between respective first and second voltages on the RF input node and the RF output node that are substantially in phase, determines current through the first transistor.

Abstract: A method of calibrating longitudinal balance for a subscriber line interface circuit includes providing a first and a second driver of a differential driver pair for driving a subscriber line. An output of each of the first and second drivers is coupled to a common output. The common output is coupled to an input of the first driver. The gain of at least one of the first and second drivers is adjusted until a calibration signal (V1) present at the input of the first driver is substantially the same as a calibration signal (V2) present at the input of the second driver.

Abstract: An adaptively tuned RF power amplifier includes at least one power amplifier stage that has one or more active elements. A tunable output network is coupled to the power amplifier stage and includes one or more adjustable reactive elements. A mismatch detector detects a tuning mismatch based, at least in part, on one or more signals present within the tunable output network, and supplies one or more mismatch signals indicative of a detected tuning mismatch. A tuning controller, responsive to the one or more mismatch signals, controls one or more of the one or more adjustable reactive elements in the tunable output network so as to control the detected mismatch.

Abstract: Methods and apparatus for coupling outgoing analog audio signals to a subscriber line are described. A subscriber line interface circuit apparatus couples an outgoing audio signal to the subscriber line through a common base isolation stage. In one embodiment, linefeed driver control signals for controlling battery feed to the subscriber line are received on the same signal lines as the outgoing audio signal. In various embodiments, the common base isolation stage comprises a plurality of bipolar junction transistors coupled in a common base configuration or a plurality of field effect transistors coupled in a common gate configuration.

Abstract: One embodiment of an apparatus for switching a transistor includes a first current mirror providing iB=K1i1, as a transistor base current, wherein the first current mirror is selectively driven by a current source i B ? ? MAX K 1 . A second current mirror providing a feedback signal i2=K2iD to the first current mirror such that i 1 + i 2 = i B ? ? MAX K 1 , wherein iD contributes to the transistor collector current, wherein iB=iBMAX?K1K2iD.

Abstract: A subscriber line interface circuit apparatus includes tip/ring sense circuitry generating a tip sense signal and a ring sense signal from three sensed currents, wherein the tip sense signal and the ring sense signal correspond to subscriber loop tip and ring currents, respectively. In one embodiment, the tip/ring sense circuitry includes a current mirror generating first and second mirrored sense currents from a first sense current proportional to a battery feed node voltage of a subscriber loop. Current differencing circuitry provides the tip sense signal from a difference between the first mirrored sense current and a second sense current associated with a tip line of the subscriber loop. The current differencing circuitry provides the ring sense signal from a difference between the second mirrored sense current and a third sense current associated with a ring line of the subscriber loop.

Abstract: One embodiment of a power supply apparatus includes a switching regulator generating an output voltage VOUT at an output node from an input voltage VIN at an input node in accordance with a pulse width modulated signal having a nominal frequency of fs. A pulse width modulator provides the pulse width modulated signal in accordance with a pulse control signal. A digital control loop sampling the second voltage to provide an m-bit sampled value at a sampling rate, f1. The digital control loop includes a loop filter providing a filtered value from the sampled value and a delta sigma modulator sampling the filtered value as an n-bit value at a frequency f2 to provide the pulse control signal, wherein m>n.

Abstract: One embodiment of an apparatus for switching a transistor includes a first current mirror providing iB=K1i1, as a transistor base current, wherein the first current mirror is selectively driven by a current source i B ? ? MAX K 1 . A second current mirror providing a feedback signal i2=K2iD to the first current mirror such that i 1 + i 2 = i B ? ? MAX K 1 , wherein iD contributes to the transistor collector current, wherein iB=iBMAX?K1K2iD.

Abstract: One embodiment of a power supply apparatus includes a first switcher coupled to provide VOUT from a VSUPPLY. A cascaded second switcher is coupled to provide a subscriber line interface circuit target VBAT from VOUT, wherein the first switcher is placed in one of an active mode and an inactive mode in accordance with a function of VSUPPLY and VBAT, wherein in the active mode ? VOUT VSUPPLY ? ? 1 , wherein in the inactive mode VOUT?VSUPPLY.

Abstract: An adaptively tuned RF power amplifier includes at least one power amplifier stage that has one or more active elements. A tunable output network is coupled to the power amplifier stage and includes one or more adjustable reactive elements. A mismatch detector detects a tuning mismatch based, at least in part, on one or more signals present within the tunable output network, and supplies one or more mismatch signals indicative of a detected tuning mismatch. A tuning controller, responsive to the one or more mismatch signals, controls one or more of the one or more adjustable reactive elements in the tunable output network so as to control the detected mismatch.

Abstract: Methods and apparatus for coupling outgoing analog audio signals to a subscriber line are described. One method includes the step of receiving the outgoing audio signal. The outgoing audio signal is coupled to the subscriber line through a plurality of transistors coupled in a common base configuration. In one embodiment, linefeed driver control signals for controlling battery feed to the subscriber line are received on the same signal lines as the outgoing audio signal. A subscriber line interface circuit apparatus includes a first circuit for coupling a received outgoing audio signal to a subscriber line. The first circuit couples the received outgoing audio signal to the subscriber line through a common base isolation stage. In various embodiments, the common base isolation stage comprises a plurality of bipolar junction transistors coupled in a common base configuration or a plurality of field effect transistors coupled in a common gate configuration.

Abstract: A method includes the step of providing subscriber loop pull-down circuitry operating in a first voltage domain. The subscriber loop pull-down circuitry decreases at least one of a tip and a ring line current in response to a corresponding pull-down control signal. The method further includes the step of providing control circuitry operating in a second voltage domain, wherein the first and second voltage domains are substantially distinct. The control circuitry varies the pull-down control signal to decrease a selected one of the tip and ring line currents in response to a sensed current corresponding to an associated one of a tip pull-down current and a ring pull-down current. A subscriber line interface circuit apparatus includes pull-down circuitry operating in a first voltage domain. The pull-down circuitry varies line currents of the tip and ring lines in response to a pull-down control signal provided by control circuitry operating in a second voltage domain.

Abstract: A method of calibrating longitudinal balance for a subscriber line interface circuit includes providing a first and a second driver of a differential driver pair for driving a subscriber line. An output of each of the first and second drivers is coupled to a common output. The common output is coupled to an input of the first driver. The gain of at least one of the first and second drivers is adjusted until a calibration signal (V1) present at the input of the first driver is substantially the same as a calibration signal (V2) present at the input of the second driver.

Abstract: A subscriber line interface circuit apparatus includes a signal processor having sense inputs for a sensed tip signal and a sensed ring signal of a subscriber loop. The signal processor generates at least one linefeed driver control current in response to the sensed signals. The signal processor is not a predominant source of any of a tip current or a ring current of the subscriber loop.