National Semiconductor Corporation

William M Howard

Thomas M Frederiksen

Robert S Sleeth

Dennis M Monticelli

A communication system for providing both analog information pulses and digital information pulses in a single frame of a pulse train, including circuitry for sequentially multiplexing and modulating a first given number 'm' of analog information input channels to provide 'm' analog information pulses in each frame of the pulse train to convey information respectively representative of the analog information in the analog information input channels; and circuitry for modulating a second given number 'n' of binary information input channels to provide a variable number of digital information pulses and for multiplexing the variable number of digital information pulses in each frame of the pulse train sequentially to the analog information pulses, wherein the variable number of digital information pulses is within a range of 2.sup.n pulses to convey information respectively representative of the binary information in the 'n' binary information input channels. A system for producing analog information signals and binary information signals from such a pulse train includes a binary counter for counting the number of information pulses in each frame of the pulse train; 'm' gates coupled to given stages of the counter for producing 'm' analog information signals respectively conveying the analog information conveyed by the 'm' analog information pulses in each frame; and 'n' gates coupled to given stages of the counter for producing 'n' binary information signals containing binary information that is representative of the number of digital information pulses included in the count for each frame. The counter is reset by a sync pulse included in each frame of the pulse train the binary information is read from the counter in response to the sync pulse to produce the binary information signals.

Simultaneous communication of analog and binary information in a single

An improved comparator circuit is employed to respond to the charge on a capacitor which represents the integrated value of an input current. When the charge exceeds the comparator trip point, an output is generated. The output is delayed in time from the onset of the input current by an amount that is almost exactly linearly proportional to the current magnitude. The improvement comprises a circuit that senses the onset of comparator conduction and supplies the current necessary to operate the comparator. At very low input current values a condition can be reached where the current drawn by the comparator input equals or exceeds the applied current. For this condition an ordinary comparator will never trip. The improved circuit prevents this and, since the current added is only to compensate, the timing function is not seriously perturbed.

Extended range current-to-time converter

A differential amplifier has one input connected to a reference potential and a photo diode connected in series with a level shift to the other input. A negative feedback loop is also coupled into other input. This stabilizes the amplifier and, if the level shift is made equal to the reference potential, biases the photo diode to zero, thereby reducing leakage current. A second feedback loop is used to adaptively bias the tail current in the differential amplifier.

Adaptively biased differential operational amplifier for photo diode

A sonar system utilizing a common LC tuned circuit for both the transmitter portion and the receiver portion of the electronic system so that both receiver and transmitter are tuned to the same frequency. The transducer is isolated from the LC tuned circuit so that the impedance characteristics of the transducer will not operate to change the main frequency of the tuned circuit. Thus interchangeable transducers may be utilized with the receiver-transmitter circuitry. The transmitter power pulses are generated by a novel Class C pulse circuit providing short time width, high intensity power pulses to the transducer.

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Campbell, CA, United States of America

William M Howard