A nonintegrating, high sensitivity, wide dynamic range receiver is described. A voltage dependent current source is connected in negative feedback with a forward voltage amplifier. The transconductance of the current source is essentially independent of frequency within the signal bandwidth frequency, and the feedback pole is the dominant pole in the loop gain. To prevent saturation by high intensity input signals the receiver is combined with a range extender circuit.

Nonintegrating lightwave receiver

An audio system employs a microcontroller to supervise the operation of an audio system including a digitally controlled audio processor which controls at least a wideband and a narrowband gain for the audio signal. The narrowband gain may preferably comprise a bass boost to the audio signal. Clipping distortion of the audio signal is avoided by sensing clipping in a power amplifier and reducing the digital commands for the wideband gain and the narrowband gain according to a method which reduces narrowband gain in preference to the wideband gain. After the narrowband gain is reduced to a predetermined gain, the wideband gain may be reduced if clipping persists. When clipping ceases, the narrowband gain is likewise restored to its original gain in preference to restoring of the wideband gain.

Digitally controlled audio amplifier with voltage limiting

An audio system having a main chassis including an audio preamplifier and a remote chassis including a power amplifier has a clipping level detector circuit in the remote chassis for detecting the onset of clipping by the power amplifier and has a gain control element in the main chassis for controlling the gain of the preamplifier. An extra control line in the wiring harness connecting the main chassis and the remote chassis is avoided by multiplexing the clipping signal and the mute control signal on a single control wire.

Audio limiter using voltage multiplexed feedback

A circuit and method are provided for generating a clipping distortion detector output signal for an integrated circuit audio amplifier which is independent of operating temperature and supply voltage. The system includes an audio amplifier having a voltage gain, a first input for receiving an input voltage and an output for generating an amplified output voltage. A supply voltage is supplied to the audio amplifier and the supply voltage determines the maximum amplified output voltage. A comparison voltage is generated which is indicative of the output voltage divided by the voltage gain. A clip detector voltage comparator receives the input voltage and the comparison voltage and provides a clipping distortion detect signal when the input voltage deviates from the comparison voltage in excess of an offset voltage which is indicative of detection of excessive clipping distortion. According to one embodiment, the offset voltage is adaptively controlled as a function of the supply voltage so as to maintain a substantially constant maximum percent distortion. According to a second embodiment, the offset voltage is adjusted as a function of supply voltage to achieve an adjustable maximum percent distortion. In addition, the offset voltage is also controlled as a function of temperature to provide temperature compensation. The supply voltage and temperature compensation may be achieved by generating a current source as a function of supply voltage and temperature.

Amplifier clipping distortion indicator with adjustable supply dependence

In an amplifier stage comprising a pair of input current sources, connected in series between a pair of reference potential lines, a pair of output transistors connected between the pair of reference potential lines and defining an intermediate output terminal of the amplifier, a driving circuit comprising active elements and interposed between the input current source and the output transistors, and at least one saturation control circuit comprising at least one control transistor connected with its base to the driving circuit and with its collector and emitter between the output of the amplifier stage and the intermediate point between the input current sources, to detect distortion due to clipping, at least one distribution detection transistor is provided, connected to the control transistor so as to detect the current flowing through the latter, which current is related to the imbalance of the input current sources and therefore to the distortion generated in the stage.

High-dynamics amplifier stage with distortion detection

A differential amplifier is connected to an amplifier for comparing an amplifier input signal with the signal fed back by the amplifier feedback circuit. The output of the differential amplifier is coupled to a full wave rectifier the output of which controls an attenuator connected between a source of electrical input signals and the amplifier. When the amplifier is operating in its linear range, the differential amplifier inputs are identical and it does not produce an output. Under this condition, the input signal is not attenuated. However, in the presence of amplifier clipping, the differential amplifier produces an output which, after full wave rectification, operates to increase the attenuation, and thus reduce the amplitude of the signal applied to the amplifier; clipping is limited.

Amplifier improvements for limiting clipping

In an amplification system comprising an amplifier, a loudspeaker, normally open contacts connected in series between the amplifier and the speaker, and a power supply for the amplifier having relatively long buildup and decay times of its output voltage in response respectively to the connection and disconnection of the power supply to and from the a.c. line, means are provided responsive to the connection of the power supply to the a.c. line for delaying the closing of the normally open contacts until after the power supply voltage has built up to its full operating potential for eliminating the transient audio signals from the amplifier associated with power supply voltage buildup from being reproduced by the loudspeaker. Means are also provided for opening the contacts quickly after the power supply is disconnected from the a.c. line for eliminating the distorted audio signals from the amplifier associated with power supply decay from being reproduced by the loudspeaker. Additionally, if the amplifier is of the balanced type which exhibits a zero d.c. output potential during normal operation, means are provided for quickly opening the contacts upon the occurrence of a high d.c. amplifier output potential of either polarity for protecting the loudspeaker.

Protective system for stereo loudspeakers

A superheterodyne f.m. receiver having a manually tunable local oscillator which is electronically voltage tunable over a small range, and including a frequency discriminator for providing signal voltage and a.f.c. voltage in response to a received f.m. carrier, wherein is provided an electronic bipolar switch responsive to either positive or negative a.f.c. voltage of greater than a predetermined value for effecting grounding of a point of an a.f.c. circuit which applies a.f.c. voltage to the local oscillator, and which also includes an interchannel noise detector which also provides grounding signal for that same point of the a.f.c. circuit.

Ronald C. Evans

Papers

Amplifier improvements for limiting clipping

Protective system for stereo loudspeakers

Automatic frequency control system