Abstract: An operational amplifier includes a differential amplifier circuit provided at an input stage and an amplifier circuit at a post stage. In the differential amplifier circuit, first and third bipolar transistors are PNP-type bipolar transistors and Darlington-connected. An inverting input terminal is connected to the base terminal of the first bipolar transistor. The first and third bipolar transistors and second and fourth bipolar transistors construct an input differential pair. First and second protection diodes are connected between the base terminals of the first and second bipolar transistors constructing the input differential pair and the ground potential, respectively. Each of the protection diodes is connected so that the cathode terminal is positioned on the base terminal side of the bipolar transistor, and the cathode terminal is positioned on the ground potential side.

Abstract: A radio-frequency power amplifier for preventing a final-stage HBT from being destroyed is provided. To this end, a radio-frequency multistage power amplifier of the present invention includes: a first amplification stage having a first hetero bipolar transistor of which collector output is detected; a second amplification stage which is prior to the first amplification stage and which has a second hetero bipolar transistor in which the detection result is reflected; a first resistor provided between a collector of the second hetero bipolar transistor and a power supply; and a protection circuit which is connected between a collector of the first hetero bipolar transistor and the collector of the second hetero bipolar transistor, detects output from the collector of the first hetero bipolar transistor, and reduces a voltage of the collector of the second hetero bipolar transistor in accordance with the detected output.

Abstract: In one embodiment, the present invention includes an amplifier having an input to receive a radio frequency (RF) signal from an output node of a source. An input stage coupled to the amplifier input may include one or more components to aid in processing of incoming signals. One such component coupled between the source and the input of the amplifier is a coupling capacitor used to maintain a bias voltage of the amplifier at a different potential than a DC voltage of the output node. In certain applications, the amplifier and the coupling capacitor may be integrated on a single substrate.

Abstract: The invention relates to a current limiting method, e. g. for Class D amplifiers comprising a unique detection- and control method. The current detection circuit can be implemented as a voltage measurement where the measured voltage corresponds to the current flowing through the power-switching device. The device can be switched OFF when a set limit is reached. By forcing certain OFF time, the associated control system behaves as a self-oscillating current limiting circuit. This can be implemented locally close to the switching device and be independent of other local or global control systems.

Abstract: An amplifier circuit includes a first circuit and a second circuit connected in series. The first circuit has a first terminal coupled to a first power supply terminal, a second terminal coupled to an output node, and a control terminal for receiving a first signal for controlling a current flow. The second circuit has a first terminal coupled to the output node, a second terminal couple to a second power supply terminal, and a control terminal for receiving a second signal controlling a current flow in the first circuit. A bias circuit is coupled to the third terminal of the first circuit and is configured to limit a current flow in the first circuit when a voltage at the output node is outside a predetermined voltage range. In an embodiment, the bias circuit includes a plurality of diode devices connected in series and a switch device coupled to the diode devices.

Abstract: Methods and apparatus to reduce voltage bounces and spike voltages in switching amplifiers are disclosed. An example apparatus to reduce spike voltages in a switching amplifier disclosed herein comprises an input to sense an output voltage of the switching amplifier, and a pull-down circuit to electrically couple the apparatus with a transistor in the switching amplifier, wherein the pull-down circuit is configured to vary in strength based on the output voltage sensed by the input.

Abstract: An apparatus and method is disclosed for providing control of current consumption of a power amplifier. The power amplifier comprises an output stage for amplifying a RF signal, and the output stage is operably coupled to an output load. The power amplifier further comprises a bias circuit operably coupled to the output stage, wherein the bias circuit is capable of applying a bias voltage to the output stage. The power amplifier still further comprises a limit circuit operably coupled to the bias circuit for detecting an increase in the current of the output stage under an output load mismatch and in response, decreasing the bias voltage applied to the output stage.

Abstract: An amplifier can advantageously use a power supply voltage source that provides a voltage greater than all breakdown voltages of the process associated with transistors of the amplifier. Specifically, cascoded configurations can be used to reduce the gate-drain and source-drain voltages of “at-risk” transistors in the amplifier. During a power down mode, a bias shunt of the amplifier can isolate certain nodes from the voltage sources. At the same time, a charge circuit of the amplifier can charge those nodes to a predetermined voltage, thereby minimizing stress to the at-risk transistors during the power down mode. A multi-flavor power down signal generator circuit can advantageously generate the appropriate power down signals for driving various transistors of the amplifier during the power down mode.

Abstract: One embodiment of an apparatus for testing an amplifier includes an amplifier having a driver and a filter, the filter being connected between an output of the driver and an output of the amplifier. The filter is operable to produce a demodulated output signal from a higher frequency modulated signal at the driver output. The apparatus also includes a voltage level detector connected to the driver output and a control circuit operable to detect at least one fault based on a voltage level measured at the driver output by the voltage level detector.

Abstract: Methods and apparatus for enabling auto-recovery of a digital audio amplifier after a short-circuit are disclosed. In accordance with one embodiment, a short-circuit is detected by both detecting a switching signal at an output of the digital audio amplifier and sensing a mute signal coupled to the digital audio amplifier. Once a short-circuit has been detected, a reset signal is provided to a reset input of the digital audio amplifier when the switching signal indicates that the digital audio amplifier is not switching and the mute signal indicates that the amplifier is in an un-muted state.

Abstract: There is provided a low-cost loudspeaker system which can adjust attenuation and provide protection against an excessive input. Between input terminals and a loudspeaker unit is provided a serial circuit including a plurality of resistor elements. A switch is provided which can switch between connected and disconnected states of two points, which includes one or more resistor elements of the serial circuit therebetween, through an over-current protection element.

Abstract: A power amplifier drives a load connected to a first output terminal and a second output terminal. When generation of over-current is detected by the current detection section, the output amplifier control section is controlled to stop the operation of the output amplifier section, and when a voltage greater than or equal to said set value is detected by said voltage detection section, the stopped operation of said output amplifier section is maintained even though generation of the over-current is not detected at the current detection section. When the terminal voltage detection section detects a terminal voltage greater than or equal to a predetermined voltage, over-current at the current detection section is suppressed.

Abstract: An apparatus and method are provided for reducing the output voltage in a power amplifier. The power amplifier contains a power supply, an amplifier stage, an impedance matching circuit, and a voltage reduction unit connected between the power supply and the amplifier stage. A power amplifier device within the amplifier stage has a gain bandwidth that covers multiple frequency bands. The output voltage of the power amplifier device is a composite voltage that contains fundamental and harmonic components that lie within the gain bandwidth. The voltage reduction unit reduces the supply voltage of the power amplifier device such that the composite output voltage is less than the breakdown voltage in the power amplifier device. The impedance matching circuit is coupled to the power amplifier device output and provides impedance matching for output signals of the fundamental and harmonic frequencies.

Abstract: An amplifier for improving an electrostatic discharge (ESD) characteristic includes an operational amplifier, a first resistor circuit, a first fuse box, a second resistor circuit, and a second fuse box. The operational amplifier includes a first input terminal receiving a first input signal, a second input terminal receiving a second input signal, and an output terminal outputting an output signal. The first resistor circuit is connected between the second input terminal and a first node to prevent ESD from being input to the second input terminal. The first fuse box is connected between the first node and the output terminal of the operational amplifier. The second resistor circuit is connected between the second input terminal and a second node to prevent ESD from being input to the second input terminal. The second fuse box is connected between the second node and a terminal for receiving a ground voltage.

Abstract: A power supply for providing a modulated output voltage to a load is disclosed. According to various embodiments, the power supply comprises a plurality of parallel-connected switch-mode power modules and a controller. The controller is connected to each of the power modules and is for controlling the duty cycles of the respective power modules such that the power modules have a common duty cycle in steady state, but in a phase-shifted or “interleaved” manner. In addition, the controller is for controlling the output voltage of the power converter by controlling the ratio of power modules in the forward state at a time to the total number of power modules. In this way, by providing a sufficiently large number of power modules, arbitrarily low output voltage amplitudes and intra-level oscillations can be achieved. Further, the rate of modulation of the output voltage can exceed the switching frequency (f=1/T, where T is the switching period) of the power modules.

Abstract: A power amplifier including an active device having at least one heterjunction bipolar transistor based on a compound semiconductor; a diode connected between the base and the emitter of the bipolar transistor in reverse direction with respect to the base-emitter diode; a resistor connected in series between one electrode of the diode and the base of the bipolar transistor; and a bias circuit connected between the diode and the resistor, wherein the bipolar transistor includes a plurality of transistors, and each transistor is connected to the bias circuit via a resistor connected to a base of the transistor. The bias circuit may include an emitter follower circuit having a bipolar transistor.

Abstract: A pulse modulation type electric power amplifier includes a pulse modulator that receives as input a clock and an input signal, and converts the input signal to a pulse train, an output control circuit that receives as input the pulse train output by the pulse modulator, and controls output of the pulse train, an output circuit that performs switching according to the pulse train output by the output control circuit, a comparator that converts an output terminal voltage of the output circuit to a high or a low digital value, and a short-circuit determination circuit that determines whether an output short circuit has occurred based on a state of an output signal of the comparator, and outputs an output prohibition signal to the output control circuit when an output short circuit is detected. The output control circuit controls output of the pulse train when the output prohibition signal is input, so that the output circuit stops the switching operation.

Abstract: A thermal overload protection circuit and method for protecting switching power amplifier circuits provides protection against latch-up and other failures due to energy returned from an inductive load when the amplifier output is disabled in response to a thermal overload condition. Upon detection of a thermal overload condition, rather than immediately disabling the switching power output stage, the switching power output stage is driven toward a fifty-percent duty cycle of operation for a predetermined time period so that energy stored in inductance of the load is reduced, preventing back-currents that would otherwise may cause latch-up within the integrated circuit when the switching power output stage is disabled. After the time period has elapsed, the switching power output stage is disabled. Alternatively, the current through the inductive load is measured and the switching power stage is disabled after the magnitude of the current has fallen below a threshold.

Abstract: An automatic-gain control circuit includes a variable-gain amplifier, a peak-detecting circuit, and an adjustable charge/discharge circuit. The variable-gain amplifier receives an input signal and adjusts the input signal based on a gain-factor control signal for generating a corresponding output signal. The peak-detecting circuit is coupled to the variable-gain amplifier for generating a comparing signal according to a reference signal and the output signal. The adjustable charge/discharge circuit is coupled to the peak-detecting circuit and the variable-gain amplifier for outputting a charge current or a discharge current based on the comparing signal, thereby generating the gain-factor control signal. The ratio between the charge current and the discharge current is adjustable.

Abstract: An amplifier for improving an electrostatic discharge (ESD) characteristic includes an operational amplifier, a first resistor circuit, a first fuse box, a second resistor circuit, and a second fuse box. The operational amplifier includes a first input terminal receiving a first input signal, a second input terminal receiving a second input signal, and an output terminal outputting an output signal. The first resistor circuit is connected between the second input terminal and a first node to prevent ESD from being input to the second input terminal. The first fuse box is connected between the first node and the output terminal of the operational amplifier. The second resistor circuit is connected between the second input terminal and a second node to prevent ESD from being input to the second input terminal. The second fuse box is connected between the second node and a terminal for receiving a ground voltage.

Abstract: Two transistors of a class D output stage are driven by complementary, variable duty cycle signals PWM+ and PWM?. When the pulse width of the PWM+ signal becomes too narrow for reliable operation of prior art over-current protection circuits sensing the drain to source voltage of FET1 driven by PWM+, a Narrow Pulse Detector generates a signal indicative of this narrow pulse condition. A Negative Current Sense circuit measures the drain to source voltage across FET2 during the much longer conduction time of FET2 driven by PWM?. Because of the energy stored in the series inductor coupled to the output of the class D stage, a negative current flows through this FET2 during its conduction time. The resulting drain to source voltage of FET2 is measured and compared to a threshold. If the voltage indicative of current is over the threshold, and the Narrow Pulse Detector output indicates a narrow pulse condition, then an inhibit signal is generated which reduces current.

Abstract: A power amplification device includes a BTL amplification circuit including a first amplification circuit and a second amplification circuit, the first amplification circuit including a first output transistor, a first power detection circuit, a second output transistor, and a second power detection circuit, the second amplification circuit including a third output transistor, a third power detection circuit, a fourth output transistor, and a fourth power detection circuit, a first comparator which compares output values of the first and fourth power detection circuits, and a second comparator which compares output values of the second and third power detection circuits.

Abstract: An over-current protection circuit protection circuit and method for protecting switching power amplifier circuits provides protection against latch-up and other failures due to energy returned from an inductive load when one or more transistors in the amplifier output are disabled in response to an over-current condition. Upon detection of an over-current condition, the transistor corresponding to the over-current conduction direction is disabled. At the same time, the transistor corresponding to the conduction direction opposite the over-current direction is enabled for a predetermined time period, or until the magnitude of the load current has dropped, so that energy stored in inductance of the load is reduced, preventing back-currents that would otherwise cause latch-up and consequent destruction of the output stage when the switching power output stage is disabled. After the predetermined time period has elapsed or the load current has dropped below a threshold, the entire output stage is disabled.

Abstract: Saturation handling for preventing a power amplifier from going into a saturation condition is disclosed.

Abstract: The present invention discloses a voltage detection type overcurrent protection device, which applies to the output stage of a CMOS Class-D audio amplifier. Generally, a Class-D audio amplifier is used to drive a high-load loudspeaker; therefore, it needs a high-current driver. When there is a short circuit in the load, the high current will burn out the driver stage. The present invention detects the output voltage to indirectly monitor whether the output current is too large. Once an overcurrent is detected, the output-stage transistor is turned off to stop high current lest the circuit be burned out.

Abstract: An EER high frequency amplifier wherein the dynamic range of the gain can be widened by performing a predetermined control of a device in a high frequency amplifying part and thereby enhancing the isolation within the device. In an EER high frequency amplifier (1), an envelope detecting part (2) extracts an amplitude signal from an input high frequency signal, while a limiter (3) extracts a phase signal therefrom. A baseband amplifying part (4) generates a voltage in accordance with the amplitude signal and supplies it as the drain voltage of a GaAs FET (5a) of a high frequency amplifying part (5). When the drain voltage is below a predetermined first reference voltage, a gate voltage control part (6) holds an initially established gate voltage. When the drain voltage exceeds the first reference voltage, the gate voltage control part (6) so controls the gate voltage as to be proportional to the drain voltage.

Abstract: An operational transconductance amplifier is configured with an asymmetric output current capability. When current sunk from the output exceeds a rated load, the normally equal input voltages diverge. A comparator coupled to the OTA inputs senses when the output current drain exceeds the rated load and changes state when the OTA input voltages diverge. When used in conjunction with a current mirror transistor of known proportion, current through an output transistor, such as quiescent current through the output stage of a class A/B amplifier, can be accurately detected. A current source in parallel with the OTA output can be used to offset the current sensing trigger point.

Abstract: An operational amplifier includes a differential amplifier circuit provided at an input stage and an amplifier circuit at a post stage. In the differential amplifier circuit, first and third bipolar transistors are PNP-type bipolar transistors and Darlington-connected. An inverting input terminal is connected to the base terminal of the first bipolar transistor. The first and third bipolar transistors and second and fourth bipolar transistors construct an input differential pair. First and second protection diodes are connected between the base terminals of the first and second bipolar transistors constructing the input differential pair and the ground potential, respectively. Each of the protection diodes is connected so that the cathode terminal is positioned on the base terminal side of the bipolar transistor, and the cathode terminal is positioned on the ground potential side.

Abstract: A signal amplifier circuit includes a negative feedback amplifier circuit having an output terminal, a first voltage limiting device for limiting the output voltage from the negative feedback amplifier circuit, a second voltage limiting device for limiting the output voltage from the negative feedback amplifier circuit, a first reference voltage supply applying a first reference voltage to the first voltage limiting device, a second reference voltage supply applying a second reference voltage to the second voltage limiting device. The first voltage limiting device is configured to fix a lower limit saturation voltage at the first reference voltage. The second voltage limiting device is configured to fix an upper limit saturation voltage at the second reference voltage.

Abstract: An amplifier with an output protection having an input stage defining a feedback node, an output stage connected to the feedback node and defining an output node supplying an output voltage, and a feedback stage connected between the output and the feedback nodes. A mirror stage is connected to the feedback node and has the same structure as the output stage, the mirror stage defining a reference node connected to the feedback stage for generating a reference voltage to be compared to the output voltage by the feedback stage. The feedback stage generates a current limitation signal fed to the feedback node when a difference between the output and the reference voltages is higher than a threshold.

Abstract: A smart protection circuit to prevent possible circuit malfunction or damage due to sudden power source voltage fluctuation is introduced. In case of quick and large voltage fluctuation in power supply, a control signal is activated to stop power transistor switching. When power supply is stable at a lower or higher operating voltage, the switching circuit is able to return to normal operation.

Abstract: A power amplifier drives a load connected to a first output terminal and a second output terminal. When generation of over-current is detected by the current detection section, the output amplifier control section is controlled to stop the operation of the output amplifier section, and when a voltage greater than or equal to said set value is detected by said voltage detection section, the stopped operation of said output amplifier section is maintained even though generation of the over-current is not detected at the current detection section. When the terminal voltage detection section detects a terminal voltage greater than or equal to a predetermined voltage, over-current at the current detection section is suppressed.

Abstract: A saturation detection and warning circuit having an adaptive threshold voltage is disclosed. The disclosed circuit can also be used to detect the impending drop out of the low drop out linear voltage regulator. A clamp circuit that clamps the amplifier's output voltage at a voltage that is separated from the adaptive threshold of the saturation detector and warning circuit by a controlled offset voltage is also disclosed.

Abstract: A circuit and method for protecting a radio frequency power amplifier against peak drain voltage. A detector circuit has an input connected to a drain of a power transistor of an amplification stage of the power amplifier to detect a peak drain voltage therefrom. The detector circuit outputs a protection signal when the detected peak drain voltage exceeds a predetermined reference level. A shutdown circuit is coupled to the detector circuit and inputs the protection signal therefrom. The protection signal is used to remove a gate bias of at least one amplification stage of the power amplifier. High frequency components are used in the detector and protection circuits to immediately reduce the drain voltage from one or more of the amplification stages.

Abstract: A high power, high frequency, solid state power amplifier system includes a plurality of input multiple port splitters for receiving a high-frequency input and for dividing the input into a plurality of outputs and a plurality of solid state amplifier units. Each amplifier unit includes a plurality of amplifiers, and each amplifier is individually connected to one of the outputs of multiport splitters and produces a corresponding amplified output. A plurality of multiport combiners combine the amplified outputs of the amplifiers of each of the amplifier units to a combined output. Automatic level control protection circuitry protects the amplifiers and maintains a substantial constant amplifier power output.

Abstract: A power protecting apparatus and method of a power amplifier for removing backward voltages and preventing a hard damage within a circuit by connecting an output terminal of a DC-DC converter with an input terminal of a filter using diodes when an excessive backward voltage is generated due to physical characteristics of an inductor within the circuit at the time of applying high power level and low power level to the power amplifier using switching devices within a power circuit in order to optimize power consumption.

Abstract: A class D amplifier includes: an amplifier that generates a digital signal for driving a load based on an input signal; an attenuator that attenuates the input signal according to an attenuation command signal; and a clip prevention controller that outputs the attenuation command signal to intermittently attenuate the input signal when the digital signal is brought into a clip state or a near-clip state.

Abstract: A radio frequency power amplifier, having a first amplifying transistor 103-1 and a second amplifying transistor 103-2, comprises a detection circuit 101 that detects an output power and outputs a voltage according to the output power, and a protection transistor 102, controlled by an output of the detection circuit 101, for shunting a current flowing into the base terminal of the first amplifying transistor 103-1. The influence of a circuit for protecting against output load abnormalities on RF characteristics is suppressed.

Abstract: A protection circuit for a power amplifier of a radio frequency transmitter includes a sensing circuit that generates a sensed signal based on an output of the power amplifier. A reference signal generator generates a reference signal. A comparator communicates with the sensing circuit and the reference signal generator and outputs a first state when the reference signal exceeds the sensed signal and a second state when the sensed signal exceeds the reference signal. A turn off circuit turns off the power amplifier when the comparator is in the second state.

Abstract: A power amplification device includes a BTL amplification circuit including a first amplification circuit and a second amplification circuit, the first amplification circuit including a first output transistor, a first power detection circuit, a second output transistor, and a second power detection circuit, the second amplification circuit including a third output transistor, a third power detection circuit, a fourth output transistor, and a fourth power detection circuit, a first comparator which compares output values of the first and fourth power detection circuits, and a second comparator which compares output values of the second and third power detection circuits.

Abstract: Saturation handling for preventing a power amplifier from going into a saturation condition is disclosed.

Abstract: A radio-frequency power amplifier for preventing a final-stage HBT from being destroyed is provided. To this end, a radio-frequency multistage power amplifier of the present invention includes: a first amplification stage having a first hetero bipolar transistor of which collector output is detected; a second amplification stage which is prior to the first amplification stage and which has a second hetero bipolar transistor in which the detection result is reflected; a first resistor provided between a collector of the second hetero bipolar transistor and a power supply; and a protection circuit which is connected between a collector of the first hetero bipolar transistor and the collector of the second hetero bipolar transistor, detects output from the collector of the first hetero bipolar transistor, and reduces a voltage of the collector of the second hetero bipolar transistor in accordance with the detected output.

Abstract: A semiconductor indicator for quantitatively diagnosing voltage conditions in high power transistor devices is provided. The semiconductor indicator includes a first transistor and a second transistor, where an electrically active periphery of the second transistor is less than an electrically active periphery of the first transistor. The transistors are thermally coupled to one another and may be in close proximity. The second transistor detects the voltage of a node on the first transistor and may be monitored by infrared imaging. The breakdown voltage characteristic of the second transistor may not substantially change as the temperature in the first transistor increases. An optional control circuit monitors and detects the output voltage of the first transistor.

Abstract: A current limiting circuit is connected to the gate (input terminal) of an amplifying transistor. The current limiting circuit includes a protecting transistor, a first protecting resistor connecting the drain to the gate of the protecting transistor, and a second protecting resistor connecting the source to the gate of the protecting transistor. The current limiting circuit limits current, so that electric power larger than the maximum electric power allowable for the amplifying transistor does not pass.

Abstract: A method and apparatus are provided for use with a power amplifier for protecting active devices on the power amplifier. A peak detector is used by control circuitry to detect the presence of a peak voltage that exceeds a threshold voltage. In response to the detection of a peak voltage, the gain of the power amplifier is reduced.

Abstract: Methods and apparatus to detect impedance at an amplifier output are described. In one example, a method of determining a relative value of an amplifier output load may include determining a current provided to the amplifier output load in response to an input signal; determining a current provided to a reference load in response to a signal based on the input signal; comparing the current provided to the amplifier output load to the current provided to the reference load; and indicating a relationship between the amplifier output load and the reference load based on the current provided to the amplifier output load and the current provided to the reference load.

Abstract: An amplifier system includes an instrumentation amplifier arrangement being designed to amplify the difference between two voltage inputs with a defined gain, and to produce a single-ended output referenced to a known reference point. A front end circuit is coupled to the instrumentation amplifier. The front end circuit is configured to include a current clamp to actively limit the current in a gain resistor of the instrumentation amplifier to prevent input currents flowing when the instrumentation amplifier is over-driven.

Abstract: Protection for the transmission of higher amplitude outputs required of differential amplifiers formed by thin oxide transistors with limited maximum voltage tolerance used where compliance with communication protocol standards requires handling voltages which may, in transition, exceed desirable levels is provided by limiting the voltage across any two device terminals under power down conditions.

Abstract: A circuit and method for protecting a radio frequency power amplifier against peak drain voltage. A detector circuit has an input connected to a drain of a power transistor of an amplification stage of the power amplifier to detect a peak drain voltage therefrom. The detector circuit outputs a protection signal when the detected peak drain voltage exceeds a predetermined reference level. A shutdown circuit is coupled to the detector circuit and inputs the protection signal therefrom. The protection signal is used to remove a gate bias of at least one amplification stage of the power amplifier. High frequency components are used in the detector and protection circuits to immediately reduce the drain voltage from one or more of the amplification stages.

Abstract: A first power source 11 for supplying a bias voltage to a gate electrode G of a field effect transistor 13, which amplifies high-frequency signals, and a second power source 15 for supplying a bias voltage to a drain electrode D of the field effect transistor 13 are provided. The protective resistance 12 is connected between the gate electrode G of the field effect transistor 13 and the first power source 11, and the bias voltage controller 14 is connected between the drain electrode D of the field effect transistor 13 and the second power source 11. Further, a voltage detector 16 is connected between both ends of the protective resistance 12 to detect a voltage drop generated between both ends of the protective resistance 12, when a rectified current flows to the gate electrode G from the drain electrode D of the field effect transistor 13.