National Semiconductor Corporation

Other

Gm Global Technolgoy Operations, Inc.

Nick M Johnson

Parviz Ghaffaripour

Arthur Joseph Kalb

Nick S Kapsokavathis

Stephen Paul Sanders

Sai L Ting

Chun F Cheah

Carl D Wright

Chun-Foong Cheah

The present invention relates to a method for over-current protection of an amplifier circuit, which comprises driving an electronic load with the output of the amplifier circuit and sensing for a fault condition in the load, such as a short or over-current condition. The amplifier is switched off in response to the fault condition and can stay off for a specified time delay and the amplifier is then switched on. The fault condition is tested for again and, if cured, the amplifier can remain on until a new fault condition is detected. If the fault condition remains, testing and switching the amplifier on and off over very short time periods results in an effectively limited current in the load.

Over-current protection technique

A system and method which generates amplified signals indicative of left and right stereo channels, and uses the signals to drive transducers for each of subwoofer, left stereo, and right stereo channels. The amplification circuitry is operable with a power supply having low peak current capability (i.e., low peak to average current rating) even when amplifying an input signal pair having highly correlated frequency components, since it spreads the peak current demands imposed on the power supply over a full cycle of each of the highly correlated frequency components. A series-connected pair of left and right channel transducers is driven by left and right channel power amplifiers of the amplification circuitry, and the subwoofer channel transducer is connected in parallel with this transducer pair so that all three transducers are driven by two power amplifiers, thus eliminating the need for a third power amplifier to drive the subwoofer channel transducer. Preferably, the system of the invention includes high pass and low pass filters which direct appropriate subsets of the frequency components of each output signals of the amplification circuitry outputs to an appropriate subset of the transducers.

Method and system which drives left, right, and subwoofer transducers with multichannel amplifier having reduced power supply requirements

An amplifier circuit with improved turn-on transient operation includes a differential amplifier and a selectively variable reference generator for controlling the amplifier output during circuit turn-on. The amplifier is biased by a single power supply and its differential inputs are driven by a reference voltage from the reference generator and a single-ended input signal. Following circuit turn-on, the selectively variable reference voltage, generated by charging the bypass capacitor with a constant current source, charges in a linear manner from ground potential toward its final value of, typically, half of the power supply voltage. This allows improved turn-on transient operation to be realized, e.g. reduced 'pops' and 'clicks' upon circuit turn-on, while giving the user increased flexibility in selecting the sizes of the reference voltage bypass capacitor and the input signal coupling capacitor.

Amplifier circuit with reduced DC power related transients

An amplifier circuit with improved turn-on and turn-off transient operation includes an amplifier and a controller for controlling the amplifier output during initial and subsequent circuit turn-on and turn-off. The amplifier is biased by a positive power supply voltage and has a differential input driven by a reference voltage and a single-ended input signal. Where the output is single-ended, a single amplifier provides a single-ended output signal. Where the output is differential, the amplifier includes cascaded, differential input, single-ended output amplifiers which together provide a differential output signal. Following circuit turn-on and turn-off, the reference voltage, which drives one of each of the differential inputs, typically charges to or discharges from, respectively, a value of half of the positive power supply voltage. Following circuit turn-on and turn-off and during initial charging or discharging, respectively, of the reference voltage, the controller forces the single-ended output signal to follow the relatively slowly charging or discharging reference voltage and the differential output signal to remain at zero. When the reference voltage is fully charged, the controller releases control and both the single-ended and differential output signals become equal to the sum of the reference voltage and a multiple of the input signal. Hence, turn-on and turn-off transients in the output signal due to circuit turn-on and turn-off are avoided.

Amplifier circuit with reduced turn-on and turn-off transients

An output stage of an amplifier contains N-channel high-side and low-side transistors for producing an output current. The gate drive circuitry for the transistors includes an N-channel transistor having its gate connected in common with the gate of the low-side transistor to the output of a high-gain input stage amplifier, and having its drain connected to the gate of the high-side transistor. This structure reduces distortion at the crossover between positive and negative output voltages and improves control of the quiescent current. Avoiding a P-channel low-side transistor also reduces the area required for the amplifier on an IC chip and eliminates clipping during negative swings of the output voltage. A capacitive coupling stage is used to prevent clipping during positive swings of the output voltage. When the gate drive for the high-side transistor goes low, a capacitor charges through a diode. When the gate drive goes high again, the diode becomes reverse-biased, and a P-channel transistor turns on to deliver the charge on the capacitor to the gate of the high-side transistor, providing a gate bias above the positive voltage rail. The capacitor can be fabricated in integrated form.

Amplified output stage containing N-channel output transistors and

A circuit for responding to the output of a capacitive fuel sensor that can distinguish gasoline from methanol and produces an output that is related to the methanol proportion. The response is independent of the conductivity in the sensor resulting from fuel contamination. A square wave is employed to excite the sensor and the circuit provides for stabilizing the square wave amplitude. The circuit includes an amplitude modulation detector that converts the square wave transients into a fuel composition related voltage output that can be applied to an engine control mechanism that will adjust the automotive engine to operate efficiently with the fuel being supplied. Circuits are shown for linearizing the fuel composition to voltage response and a charge dispenser amplitude modulation detector is described wherein the detection occurs only during the square wave transient interval.

IC for producing an output voltage related to fuel composition in a

A fuel composition sensor provides to a voltage divider comprising sensor and reference capacitors a voltage which oscillates between two voltages at a comparatively low frequency, such as 6 KHz, for lower power dissipation, but which switches fast to produce periodic fast voltage changes across the voltage divider to produce voltage spikes at the junction of the capacitors indicative of the capacitance ratio and thus of fuel composition.

Capacitive fuel composition sensor with slow oscillator and high speed

A gauge circuit for use with a wide angle air core meter display having high linearity and adapted for use with a remote sensing resistor. A constant sense current is provided and its value is moudlated at a frequency that is high with respect to the frequencies associated with offset voltages that occur with a sense resistor that is grounded remotely from the gauge ground. A low duty cycle pulse modulation shape is disclosed for the purpose of minimizing electromagnetic interference radiation.

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Los Altos, CA, United States of America

Nick M Johnson