Rohm Co., Ltd.

Jun Hirai

Kaoru Izawa

Shigeyoshi Hayashi

A delta modulation type data converter is adapted to carry out signal processing by sequentially comparing in cycles an inputted signal with a reference voltage set according to the results of previous comparisons and includes a plurality of current sources, switch circuits for setting a current value by appropriately selecting one or more of these current sources, an integrator circuit for generating the reference voltage according to a specified current value, and a control circuit for controlling the switch circuits to make an appropriate selection of these current sources according to the result of a comparison between the reference voltage and the inputted analog signal. The control circuit controls the switch circuits such that, if the result of comparison is the same as in the precious cycle, a selection from the current sources is made such that the current value will be increased, provided such selection is possible. If the result of comparison is inverted from the previous cycle, a selection is made such that the current direction with respect to the integrator circuit is reversed. If the result of comparison is inverted repeatedly for a specified plural number of cycles, a selection is made such that the current direction with respect to integrator circuit is reversed and the associated current value is reduced, provided such selection is possible. The plurality of current sources may include a first group connected to a source voltage and a second group connected to a reference voltage source, the current sources in each group having associated therewith current values which differ by a factor of 2 from one to another.

Data converters for sound equipment

An audio apparatus having a plurality of modes as a karaoke reproduction to superimpose a sound signal from a microphone on an audio signal from a stereo sound source. A subtracting circuit is provided which obtains the difference between left and right channel signals from the sound source. A first changeover circuit selectively outputs the left and right channel signals to first and second terminals in a combination in accordance with a mode. A second changeover circuit is connected to the output of the subtracting circuit and to at least one of the left and right channel signals and selectively outputs a subtraction signal and a signal on the line to which the second changeover circuit is connected, to a third terminal. A third changeover circuit selectively outputs signals at the first, second and third terminals to fourth and fifth terminals according to the modes.

Audio apparatus having a karaoke function

An analog signal to be delayed thereby is compressed according to a monotonously increasing, convex compression function and sent to a delay circuit constituted digitally. Data of a digital value stored in a memory is read out after a constant delay time and converted into an analog signal by a D/A converter. The analog signal is expanded according to a reverse function of the compression function to restore it as an echo signal.

Echo attaching circuit and audio device using the same

This invention includes a compression circuit for compress one of an audio signal and a mixture of the audio signal and an echo signal, a delay circuit for delaying an output signal of the compression circuit by a predetermined time and an expansion circuit having a conversion rate controlled by a DC voltage generated correspondingly to a regulation of the volume controller, for expanding the output signal of the delay circuit according to a reverse conversion function to the compression conversion function to generate the echo signal.

A transmission gate having a CMOS structure wherein an NMOS transistor and a PMOS transistor are connected in parallel between an input signal line and an output signal line and a separation layer which separates a transistor formation region for one of the PMOS transistor and the NMOS transistor formed in a substrate from the substrate, wherein the back gates of the respective transistors are constituted to receive an input signal from the input signal line when the one transistor and the other transistor formed in a well region are in a conductive state.

Transmission gate

As a switch circuit SW1 is incorporated in an integrated circuit, the number of IC terminals is proportionately reducible. On receiving a mute input signal Min, a mute circuit 13 generates a mute control signal M1 and subsequently a mute control signal M2 later than M1. On receiving the mute control signal M1, the switch circuit SW1 grounds the signal line of an audio output signal A, whereas on receiving the mute control signal M2, a switch circuit SW2 cuts the signal line of an audio input signal I later. A muting function can thus be fulfilled stably.

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Kyoto, Japan

Jun Hirai