Abstract: A transistor overcurrent protection circuit using an error amplifier to make a voltage comparison between a threshold voltage and the collector voltage of a current sensing transistor. The current sensing transistor is arranged in a circuit such that the collector current of the current sensing transistor is a measure of the collector current of an output transistor. A driver transistor has its emitter connected to the base of the output transistor. A source of control current to the drive transistor is coupled to the output of the error amplifier. When the collector voltage of the current sense transistor falls below the threshold voltage, the error amplifier causes the control current to the drive transistor to be reduced so as to reduce the collector current of the output transistor.

Abstract: A power control circuit for use in radio transmitters such as portable telephone sets includes a power amplifier for amplifying the power of a transmission signal to obtain an output signal; control circuits for controlling the amplitude of the signal output by the power amplifier; a limiter for partially limiting the amplitude of the signal from the power amplifier in order to obtain a limited signal; a multiplication circuit for multiplying the limited signal from the limiter and part of the signal from the power amplifier in order to acquire a multiplied signal; a low-pass filter for extracting a DC component of the multiplied signal from the multiplication circuit; and a comparison circuit for comparing the DC component from the low-pass filter with a reference voltage in order to obtain a comparison output.

Abstract: A power supply circuit provides power to an antenna amplifier (4) of a vehicle radio via the antenna bushing (A) and the antenna cable (6). The circuit is resistant to short-circuits and has a pair of signal terminals (K2, K3) from which information, about the type of attached antenna and about its operating state, can be picked up.

Abstract: An electronic circuit for automatically adjusting the operating point of an audio amplifier comprising means for sensing the current flowing in the load, coupled to a first threshold detector, said first threshold detector having a plurality of outputs, each of said outputs representing some fraction of maximum load current; a plurality of timing means, each triggered by one of the plurality of outputs from said first threshold detector, each having a time constant inversely proportional to the fraction of load current represented; means for sensing the operating temperature of the amplifier output stage devices, coupled to a second threshold detector, said second threshold detector having an output which is enabled above a certain temperature and where said output may be used to inhibit one or more of the timer means; means for detecting bias level in a pre-driver stage, coupled to a low pass filter; a error amplifier, whose inputs are coupled to said temperature sense means, said timer outputs and said low

Abstract: An amplifier comprising a power stage the output of which is compared with a reference level by a comparator. If the output exceeds the reference level, a reduction is made in the gain of a variable-gain cell upstream from the power stage. The reference level varies with temperature, and, more specifically, presents a high constant value (e.g., greater than the supply voltage) when temperature is below a predetermined threshold (e.g., 130.degree. C.), and decreases in proportion to an increase in temperature, when the temperature exceeds the predetermined threshold. Thus, the input signal is only attenuated in the event the output signal exceeds given values inversely proportional to temperature, and with no reduction in peak output at high temperature.

Abstract: The protection circuit includes a micro strip line whose length is equal to a fourth of the wavelength of an amplification signal frequency on a board and whose one side is connected to the input side of a low noise amplifier, a diode whose one side is connected to the other side of the micro strip line and whose other side is grounded, and a capacitor which is connected to the point where the micro strip line is connected to the diode and whose impedance is sufficiently small at the amplification signal frequency. In this configuration, the diode has virtually no effect to the amplification signal component because the impedance of the protection circuit for the amplification signal frequency viewed from the contact point becomes sufficiently high. In addition, for static electricity charged on the antenna connected to the input terminal, the diode is virtually connected directly to the input side of the low noise amplifier because the micro strip line is almost zero in resistance.

Abstract: Generally, and in one form of the invention, a bias circuit for a transistor amplifier comprising a nonlinear element which limits current flow in a transistor, whereby the output-signal amplitude of the transistor is limited and the transistor is protected from exceeding a maximum current level, is disclosed. In another form of the invention, a bias circuit for a transistor amplifier comprising a nonlinear element 44 which limits current flow through a base terminal of a bipolar transistor 48, whereby the output-signal amplitude of the bipolar transistor 48 is limited and current flow through a collector or an emitter terminal of the transistor 48 is prevented from exceeding a maximum safe level, is disclosed.

Abstract: A circuit arrangement for optionally amplifying one of two signals (from 2 or 6 respectively) in which at least one of the signals is supplied via a switchable signal path interruption which is inhibited when no signal is applied thereacross, and to which in this state a signal voltage is applied to both ends, which is associated with the signal to be amplified and which has already been amplified, respectively. When such a structure of a circuit arrangement is used, no damage to the circuit structure can occur, even when a signal path is interrupted in normal operation.

Abstract: Disclosed is a transmission power amplifier device comprising a GaAs power amplifier using a GaAs FET as its amplifier element. In order to compensate the non-linearity of the frequency characteristic of the transmission power amplification efficiency of the GaAs power amplifier with respect to individual amplified signal transmission channels, gate voltage information for each of the channels is stored beforehand in a memory, and a gate voltage obtained by adding a fixed voltage to an analog voltage generated on the basis of the gate voltage information read out from the memory is applied to the gate of the GaAs FET so as to flatten the frequency characteristic of the transmission power amplification efficiency.

Abstract: An amplifier arrangement includes a first amplifier (A1) having a first output terminal (5) for the connection of a first terminal of a load and having at least a first power transistor (PT1) with a main current path for carrying a first current (i1), which current (i1) is related to a first load current flowing via the first output terminal (5), a second amplifier (A2) having a second output terminal (6) for the connection of a second terminal of the load and having at least a second power transistor (PT2) with a main current path for carrying a second current (i2), which current (i2) is related to a second load current flowing via the second output terminal (6) a first circuit (M1) for generating a first signal (s1), which signal (s1) is related to the first current (i1), a second circuit (M2) for generating a second signal (s2), which signal (s2) is related to the second current (i2), a third circuit (M3) for generating at least one control signal (r1, r2), which control signal (r1, r2) is related to a sum

Abstract: An amplifier includes first and second transistors each of which has a conduction path, with first and second conduction path terminals, and a control terminal for controlling conduction through the conduction path. The amplifier also includes a current source and voltage reference terminal for being coupled to a voltage reference. A first Schottky diode has an intrinsic series resistance and is coupled between the second conduction path terminal of the first transistor and the current source. A second Schottky diode has an intrinsic series resistance and is coupled between the second conduction path terminal of the second transistor and the current source.

Abstract: An amplifier protector and method for preventing power overload of a power amplifier and destruction of transmission circuitry and printed wiring board. The protector continually monitors the peak forward and reflected voltages of the transmitter output which are proportional to the forward and reflected power. An associated processor determines whether the forward voltage is below a threshold voltage which indicates a circuit malfunction. If the circuit malfunction is detected, the processor via an automatic level control circuit turns off the power amplifier in a timely fashion to prevent damage to the transmission circuitry.

Abstract: A reception amplifier in a nuclear magnetic resonance system includes an input transistor. The base of the input transistor is connected to a protective circuit. The protective circuit shifts the voltage at the base-emitter path of the input transistor into the inhibit range only during a high-frequency transmission pulse. The voltage is produced by rectification of a fraction of the high-frequency transmission pulse. The protective circuit of the reception pre-amplifier prevents the input transistor from being gradually destroyed by an excessive base current during the transmission when voltage peaks are provided at the input.

Abstract: An AC power amplifier is disclosed for amplifying an AC input signal while limiting the current drawn by the amplifier. The amplifier includes at least one transistor having an input circuit for receiving an AC input signal as well as a DC bias voltage and an output circuit connected to the DC voltage source for drawing current therefrom during conductive periods of the transistor. The transistor exhibits the characteristic of being nonconductive when the AC input signal together with the DC bias voltage are less positive than a DC threshold voltage level and is conductive when the AC input signal and the DC bias voltage are together more positive than the DC threshold voltage level whereupon DC current is drawn by the output circuit from the DC voltage source. The DC current is sensed and a sense signal is provided having a magnitude in accordance therewith.

Abstract: Automatic Level Control (ALC) circuit having a directional coupler, for branching an output of an amplifier, and a detector, for detecting the branched output, is disclosed. When saturation of the amplifier is measured, coupling by the directional coupler is decreased and the input signal to the detector can be kept below a predetermined value.

Abstract: An RF power amplifier system is disclosed having a modulated voltage supply and fault monitoring thereof. The modulated DC voltage supply receives an input voltage as well as a modulating signal, such as an audio signal, to provide a modulated voltage which has been amplitude modulated in accordance with the amplitude variations of the modulating signal. Circuitry is provided for providing a variable reference signal which has a magnitude that varies with that of the modulating signal. A fault comparator compares the modulated signal with the variable reference signal and provides a fault signal dependent upon the comparison.

Abstract: A driving apparatus for driving an electro-acoustic transducer has a main body portion and a control information storage body which is arranged independently of the main body portion and is selectively separated from or coupled to the main body portion, as needed. The control information storage body stores a real circuit or information for setting electrical characteristics of the driving apparatus. In addition, the driving apparatus has a protection circuit for preventing a disadvantageous result of the driving apparatus and a load caused by an unstable operation and the like when the control information storage body is attached/detached to/from the main body portion or when an inappropriate control information storage body is loaded onto the main body portion.

Abstract: An amplifier circuit in which a first amplifier (A1) and a second amplifier (A2) are protected against short-circuits by a protection apparatus which includes a first device (M1), a second device (M2), a third device (M3) and a protection device (B). For this purpose the first device and the second device generate four signals (s1, s2, s3, s4) related to an equal number of currents (i1, i2, i3, i4), which currents are related to a first or a second load current in the first amplifier or in the second amplifier. In order to control the protection device (B), the third device generates at least two control signals (r1, r2) related to the signal currents (s1, s2, s3, s4), use being made of the equality of the load currents in the absence of short-circuits.

Abstract: An adaptive power amplifier system for use with VSWR loads includes an adaptive power supply that indirectly monitors the power dissipated by a RF power amplifier and adapts bias conditions of solid state components in the RF power amplifier to protect the components from excessive power dissipation typically experienced with VSWR loads, even while maintaining full forward power output.

Abstract: An RF power amplifier having amplifier protection is presented wherein an RF source supplies an RF input signal to an actuatable RF power amplifier having an on condition and an off condition for, when on, normally receiving and amplifying the input RF signal to provide an amplified output RF signal. RF current and RF voltage in the output circuit are detected. A first signal is provided from the RF current and exhibits a fixed amplitude but a frequency and phase corresponding with that of the RF current. A second signal is provided of the fixed amplitude and which corresponds in frequency and phase with the RF voltage. The first and second signals are compared so as to provide a phase signal having a magnitude dependent upon the phase difference between the first and second signals. This phase signal is then compared with a reference to provide a turn-off signal in dependence upon the comparison for purposes of actuating an RF power amplifier to its off condition.

Abstract: An electronic circuit device having a monolithic integrated power transistor is disclosed that comprises a parallel connection of a plurality of individual partial transistors (1, 2, 3, . . . , n). In order to stabilize the distribution of the sum current to the individual partial transistors (1, 2, 3, . . . , n) resistors (41, 42, 43, . . . 4n) are provided in their emitter lines. At least one of the resistors (41, 42, 43, . . . 4n) in the emitter lines of the partial transistors (1, 2, 3, . . . , n) serves as measurement resistor for producing a signal voltage proportional to the current to provide an electronic circuit device having current regulation or current limiting, as shown in FIG. 2.

Abstract: An automatic bias control for substantially eliminating crossover distortion in power amplifiers. The bias current is measured in terms of a voltage developed across a resistor in series with the output device. This voltage is processed by a bias control function consisting of a summing circuit, a peak minimum detection circuit, a voltage reference and a mixing circuit added to the output stage in a controlled feedback loop. Elements of these circuits include operational amplifiers. The bias control system is compatible with other feedback loops in the amplifier so that transient and drift control are achieved and no instabilities are introduced. The bias control operates in the presence of widely varying high level signals.

Abstract: A levelling control arrangement for an RF transmitter circuit which additionally compensates for filter ripple, i.e. frequency dependant power variations caused by the filter disposed between a transmitter amplifier and an antenna. The forward and reflected power is sampled by a dual directional coupler between the amplifier and the filter. Signals V.sub.fwd and V.sub.rev are thus obtained indicative of the forward and reflected power levels respectively. The reflected signal V.sub.rev is subtracted from the forward signal V.sub.fwd at comparator and the difference signal V.sub.diff is compared with a reference signal Vref at comparator to produce a signal V.sub.c which is used to control the gain of the amplifier in such manner that the power developed by the amplifier increases as the signal V.sub.rev increases and vice versa. To protect against excessive reflected power levels a limiter may be included which causes the power developed by the amplifier to be reduced only if V.sub.

Abstract: A power amplifier provided with overload protection responsive to the impedance of a load falling below a threshold value having a pair of power output devices connected to the load and driven through a balanced operational amplifier and transistor couplers. The operational amplifier has opposed voltage supply inputs, and each is connected through a first resistor to a voltage source and to the load through a pair of diodes connected in series opposition and a second resistor, and the junction between the diodes is connected to the base of one of the transistor couplers. A fault condition causes current to flow through the diodes lowering the potentials of the voltage supply inputs and the bias on the transistor couplers.

Abstract: An emitter-follower circuit includes a bipolar transistor of a first conductivity type operating as an emitter-follower transistor and a bipolar transistor of a second conductivity type operable as a clamping transistor. The voltage developed between the base and the emitter of the second conductivity type clamping transistor is adapted to clamp the voltage developed between the base and the collector of the first conductivity type transistor, so that such a high voltage as exceeding the breakdown voltage is not developed between the collector and the emitter of the first conductivity type transistor. The emitter-follower circuit is capable of operating with safety even when an input signal applied thereto has a wide range of direct current components.

Abstract: The amplifier includes a bridge circuit having an input circuit adapted for connection across a DC voltage source and an output circuit connected across a load. The bridge circuit includes first and second transistors for, when on, connecting the DC voltage source across the load for DC current flow therethrough in a first direction and third and fourth transistors for, when on, connecting the DC voltage source across the load for DC current flow therethrough in a second direction. The transistors are controlled by an RF signal so that they turn on and off at a frequency dependent upon that of the RF signal such that current flows from the DC source alternately in the first and second directions through the load.

Abstract: A lamp intensity control system combines the functions of the tail light, the brake light, and the turn indicator light signals into one signal for controlling a plurality of lamps in an automobile. The tail light, brake light and turn indicator light signals are combined into one signal and modulated wherein the percent of modulation determines the intensity of the brightness of the plurality of lamps. Temperature protection is provided wherein a temperature limit circuit monitors the temperature of a SENSFET and disables the SENSFET if its temperature exceeds a predetermined magnitude. Over-current and open lamp conditions are monitored by comparator circuits. An over-current condition causes the SENSFET to be disabled. An over-temperature, over-current or open-lamp condition is signaled by a fault output signal.

Abstract: An amplifier circuit having a differential amplifier, provided in a semiconductor integrated circuit is disclosed. The differential amplifier has one input connected to a reference voltage generating circuit. The voltage outputted from the reference voltage generating circuit includes a voltage fluctuation depending on the fluctuation in power-supply voltage Vcc. However, a fluctuation absorbing circuit comprising resistors 51 and 52, diodes 53 and 54, and a capacitor 55 absorbs the voltage fluctuation thereof. As a result, the change in offset voltage of the differential amplifier is prevented, resulting in an improvement of a power-supply rejection ratio.

Abstract: An RF power amplifier having improved amplifier protection. An RF source provides an RF signal to be amplified. The amplifier includes a bridge circuit having an input circuit adapted for connection across a DC voltage source and an output circuit connected across a load. The bridge circuit includes first and second transistors for, when on, connecting the DC voltage source across the load for DC current flow therethrough in a first direction and third and fourth transistors for, when on, connecting the DC voltage source across the load for DC current flow therethrough in a second direction. The transistors are controlled in response to the RF signal so that they turn on and off at a frequency dependent upon that of the RF signal and such that current flows from the DC source alternately in the first and second directions through the load. An amplifier control serves to apply a reverse bias to the second and fourth transistors to prevent them from conducting current until receipt of a turn on signal.

Abstract: A detection circuit for detecting the failure or disconnection of a sense line in an audio processing system that provides an audio output signal that drives the input of an audio power amplifier. The audio power amplifier drives a speaker. The audio processing system includes an input for receiving a first feedback signal on a sense line from the output of the power amplifier. The audio processing system is responsive to the first feedback signal to control the amount of power provided to the input of the power amplifier and thus to the speaker. The detection circuit also receives the first feedback signal. The detection circuit further receives a second feedback signal from the output of the audio processing system prior to the input of the power amplifier. The magnitude of the second feedback signal is compared to the magnitude of the first feedback signal to determine whether the sense line is providing the first feedback signal from the output of the power amplifier.

Abstract: The under voltage lockout circuit disclosed herein is useful in a switching mode power supply of the type which, in operation, powers its own regulator circuitry. The lockout circuit operates to inhibit energization of the power supply, including its own regulator, until a voltage reference is established which can control the operation of a comparator which monitors the supply voltage available to the regulator circuitry.

Abstract: An overload protection circuit for a disableable amplifier includes a sensing resistor connected to provide indication of the current supplied to the amplifier and includes logic circuitry for producing a disabling control signal for a selected time interval following detection of the overload condition of the amplifier.

Abstract: An output transistor (T.sub.1) is to be protected from damage due to excessive currents. This transistor supplies a current (I.sub.o) to a load (3) and is driven by a driver transistor (T.sub.2). The base-emitter junction of a current-sensing trnsistor (T.sub.3) is connected in parallel with that of the output transistor (T.sub.1). The collector current of transistor (T.sub.3) is a measure of the current (I.sub.o) of the output transistor (T.sub.1). A current generator (5) supplying a reference current (I.sub.ref) is coupled to the collector of the current-sensing transistor (T.sub.3). If the collector current of the current-sensing transistor exceeds the reference current (I.sub.ref) the protection circuit is activated so that the driver transistor is bottomed via an emitter-follower (T.sub.4). The base current of transistor T.sub.1 is thereby limited. Thus, the output current of the output transistor is limited to a maximum value which is substantially equal to the product of the reference current (I.sub.

Abstract: The invention teaches the placement of a plurality of conducting paths in the vicinity of the base of the final stage of a Darlington configured transistor group. When an abrupt change in carrier density occurs, such as during switching intervals, the added conduction paths facilitate the removal of carriers from the base region, thereby facilitating the turn-off process. The extra conductive paths allow a more even current density within the volume of the base during changes in carrier density.

Abstract: Differentially-connected pairs of JFETs on an IC chip are protected from ESD events by connecting respective discharge control resistors to the drains of the JFETs in such a manner as to be in series with any flow of current through either JFET.

Abstract: A device for protecting an integrated circuit against overload and short circuit currents. The integrated circuit functions such that it is alternatingly switched to an ON or an OFF state, and when in the ON state a supply current (I.sub.M) is amplified by a Darlington-connected transistor step (Q.sub.20,Q.sub.21) and is supplied to the output (OUT) of the circuit across a load resistor (R.sub.LOAD). For an OFF state of the integrated circuit no current is led to the output (OUT). A protective circuit (S) comprising a detection resistor (R.sub.SENSE) is connected in series with said load resistance (R.sub.LOAD). The protective circuit also includes a differential step (D) for sensing a voltaqge (V.sub.SENSE) across the detection resistor (R hd SENSE) and a thyristor (T). Short circuit or overload on the output (OUT) causes an overcurrent to pass through said transistor step (Q.sub.20,Q.sub.21) and through the detection resistor. The increasing voltage (V.sub.

Abstract: An RF power amplifier is operated by supplying an RF signal to the amplifier for amplification and thereby providing an output RF signal to the amplifier's output circuit which has an impedance matching output network connected in series with a load. A detector serves to detect any reflected power in the output circuit. The RF power amplifier is turned off when the detected RF power exceeds a reference level. The amplifier is protected by discontinuing the supply of the RF signal to the amplifier while it is turned off and, instead, a frequency signal is supplied to the RF amplifier having a frequency that corresponds with that of any current flowing in the output circuit.

Abstract: A circuit for protecting electronic devices which are fed from a source of dc voltage and to which a subscriber's line (ASL) is connected. In order to limit the current in the event of an overload on the subscriber's line (ASL), a MOSFET (T1) is provided as current-limiting component. The MOSFET (T1) is disconnected and re-connected periodically by means of a relaxation generator (K) when the MOSFET is in its current-limiting condition. Upon the normal operation of the circuit, the relaxation generator (K) does not operate. By proper dimensioning thereof, the time for which the MOSFET (T1) is blocked can be roughly adjusted as compared with the time in which it acts as current limiter. In this way, too great a heating of the MOSFET (T1) is avoided.

Abstract: A stand-by signal is supplied to a stand-by circuit for determining the operation condition is a normal operative mode or a stand-by mode to control the operation. An output signal of the stand-by circuit is delayed by a delay circuit. An output signal from the delay circuit is supplied to a bias circuit for generating a predetermined bias voltage. An audio signal supplied from the audio signal input terminal is amplified by an amplifier circuit based on the bias voltage from the bias circuit. When it is detected by an overcurrent detection circuit that an overcurrent flows in the amplifier circuit, supply of the bias voltage from the bias circuit to the amplifier circuit is interrupted by the protection circuit. The operation of the protection circuit is controlled by output signals from the delay circuit and the overcurrent detection circuit.

Abstract: A hot melt adhesive applicator operable at a number of selected temperatures having a portion of the circuitry for control of the applicator temperature at a point remote from the applicator body. The remotely located circuitry employs a differential amplifier and a zero crossing detector for controlling the operation of a triac which, when turned on, increases the temperature at the applicator. The operational amplifier is protected by a clamping circuit from receiving a signal, when a temperature setting is changed from a high to a low setting, that would otherwise cause the differential amplifier to provide an output required for turning on the triac which would cause a run away condition to exist.

Abstract: A transistor is protected from excessive power dissipation in the event of a shorted load condition by alternately turning the transistor off for a relatively long period of time during which a capacitor is discharged through a resistor network and turning the transistor on for a relatively short period of time during which the capacitor is charged through a diode by the voltage developed across a resistor connected in circuit with the transistor.

Abstract: The present invention relates to a device for use in an amplitude modulated RF transmitter. The device protects power transistors located in the RF transmitter particularly in the modulator and power amplifier portions of the transmitter. The device is comprised of a capacitor unit which is adpated to be charged in a first direction; a detector which detects an audio modulating signal; and a discharge unit which is connected to both the capacitor unit and the detector which selectively discharges the capacitor unit when the value of the audio modulating signal reaches a first preset level for a preset time duration during a portion of the audio modulating signal which causes positive modulation of the RF transmitter. The device also comprises a switch unit connected to the capacitor unit and which is activated when the capacitor unit discharges to a predetermined level. The switch unit is operable to remove, when activated, the audio modulating signal from the power transistors.

Abstract: A power amplifier includes an output stage comprising a pair of complementary MOSFET power transistors connected in push-pull fashion between the positive and negative poles of a split DC power supply, with the sources of the transistors connected together to ground. The input stage includes another pair of complementary MOSFET driver transistors having their gates connected together to the input signal. The drain signal of each of the driver transistors is resistor coupled to the gate of one of the power transistors, and biased so that the driver turns off as the power transistors turns on. The amplifier output signal is taken between the common point of the split DC power supply and ground.

Abstract: To permit cooling of transistor push-pull bridge-type audio end stages in car radios, where heat dissipation and cooling of components is difficult to achieve, without entire interruption of signals being amplified, the temperature of a heat sink (HS) is being sensed by a temperature sensor (14), and, if a predetermined level is exceeded as determined, for example, by a threshold circuit (15), one of the bridge arms formed by a transistor (10) is controlled to become saturated, thereby grounding-out the applied signal, so that a loudspeaker (6) will operate at only half voltage and hence 1/4 power, to thereby permit cooling of components, while providing some reproduction of introduced audio signals from an audio input terminal (11).

Abstract: A composite transistor device having over-current protection is disclosed, and particularly a device for protecting Darlington configuration power transistor devices. The over-current protection circuit operates to clamp the base-emitter potential of the exciter transistor thus causing the power output transistor to maintain a power output below a predetermined threshold value. This allows the control of the power output intensity so as to avoid damage to the circuit, and with a minimum of power losses due to active voltage losses.

Abstract: A short circuit limiter having at least one current sink transistor connected to a trip point voltage setting resistor. The trip point voltage setting resistor receives a current which is a function of a reference current. One of the current sink transistors has a base connected above the tip point voltage setting resistor. The emitter of one of the current sink transistors sets the trip point voltage and is connected to the output transistors. If there is a short circuit in a load, the increased current will cause the voltage connection between the output transistors and the current sink transistors to rise up to the trip point voltage at which point, base drive current will be diverted away from the output transistors and through the current sink transistors.

Abstract: A monolithic integrated circuit (IC) chip in which is formed a multi-driver power circuit, with each driver circuit including one output power transistor, is partitioned such that the power transistor of each driver circuit, formed in the IC, is spaced apart from those of any other driver circuit a distance sufficiently large to ensure the generation of a temperature differential between the power transistors of the different driver circuits when their power dissipation is different. A thermal sensor is formed in close proximity to each output power transistor, and as far away as possible from the other power transistors of the IC, whereby each thermal sensor is thermally, tightly, coupled to its associated power transistor. Each thermal sensor is electrically coupled to the base of its associated power transistor for controlling the conductivity of its associated power transistor when the power dissipation of its associated power transistor and its resulting temperature exceeds a predetermined level.

Abstract: A class A bridge topology for audio amplifiers configured to operate in constant current mode, comprising power stages (3,4,5,6) supplied by supplies (8,9) and driven to equal amplitude opposite phase output signals applied across a load (7). Symmetrical current conditions are placed on said power stages to achieve a cancellation of supply currents during signal application to the load. Supplies are current limited to afford non-intrusive protection against overstress.

Abstract: An FET amplifier circuit is provided capable of minimizing the phase change of signals which pass through the circuit. Further, an FET amplifier circuit is provided capable of protecting the circuit against the effects of over-amplitude input signals with the phase change minimized.

Abstract: An amplifying circuit for amplifying a bipotential input signal, including an insulating housing having a conductive input contact mounted on the housing and adapted to engage a human body so that the bipotential input signal applied to the contact; a lead amplifier having inverting and non-inverting inputs, one of which is coupled to the input contact, and an output; first and second diodes connected in parallel inverse polarity across the inputs of the lead amplifier; third and fourth diodes connected in parallel inverse polarity from the inverting input of the lead amplifier to a circuit common potential; and an output resistor connected from the inverting input to the output of the lead amplifier. Portions of the input contact are surrounded by a voltage drive shield connected to the output of the lead amplifier.