Abstract: A synchronously driven linear power amplifier (6) parallel to class D power amplifier (2) achieves an active filter equivalent, minimizing the scale of the passive filter (3), and effectively suppressing high frequency noise. Signal delay introduced by the passive filter (3) is also compensated by means of a phase compensation circuit (7) for phase compensating an audio signal applied from a signal input terminal (21).

Abstract: Two bipolar transistors formed on a common semiconductor substrate are separated by a separation band. The separation band includes a first separation portion having the same conductivity type, and substantially the same impurity concentration and diffusion depth as those of each of base regions of the bipolar transistors, and second separation portions, formed on both sides of the first separation portion, which have the same conductivity type and substantially the same impurity concentration and diffusion depth as those of each of emitter regions. The second separation portions are formed so as to be shallower than the first separation portion. The second separation portions are formed across the first separation portion in a deeper portion of the substrate and a collector region. The second separation portions enclose the respective transistors, and the first separation portion separates the transistors from each other.

Abstract: A parallel, synchronously driven linear power amplifier (6) and class D power amplifier (2) form an equivalent active filter, minimizing the scale of the passive filter (3), and effectively suppressing high frequency noise. First to third muting circuits (17-19) are used when the power supply is turned on and off to interrupt signal supply from the signal input terminal, and control operation of the class D power amplifier (2) and linear voltage amplifier (15), thereby preventing extraneous irritating noises such as popping sounds from a loudspeaker.

Abstract: A hybrid IC device with a wide dynamic range comprises two monolithic ICs, wherein the base electrode terminal of an npn transistor having the base potential which is the closest to the lower-limit potential in the operating range of the monolithic IC is connected to the base electrode terminal of a pnp transistor having the base potential which is the closest to the upper-limit potential in the operating range of the monolithic IC, the base electrode terminals and the substrate electrode terminals of the monolithic ICs are connected via constant voltage sources provided in the monolithic ICs, and supply electrode terminals and intake electrode terminals are, respectively, connected, thus linking the two monolithic ICs together.

Abstract: A power amplifier arrangement for amplifying audio signals to be applied to a number of speakers has a plurality of power amplifiers. A level detector detects a level of a peak value of outputs from the power amplifiers, and produces a control signal when the positive peak value exceeds a predetermined positive level. Two power sources are provided for providing a high voltage power and low voltage power to the speakers. A power transistor turns on in response to the presence of the control signal to provide the high voltage power to the speaker, but turns off in response to the absence of the control signal to provide the low voltage power to the speaker. A temperature detector detects a temperature of the power transistor and produces a disabling signal when the detected temperature is greater than a predetermined temperature to disable the power transistor by switching transistor.

Abstract: A temperature protected power transistor circuit for preventing thermal breakdown of a power transistor is disclosed. The temperature protected power transistor circuit has a silicon power transistor of which the base area and emitter area are formed in a double diffusion process, and a temperature detection transistor having a specific area and formed in the same silicon chip as the silicon power transistor with the base-emitter area of the temperature detection transistor 3 electrically insulated from the silicon power transistor. The base terminal and emitter terminal of the temperature detection transistor are connected to a discrete IC 12. A base-emitter voltage detector detecting that the base-emitter voltage has reached a predetermined voltage, and a bias resistor for adjusting the base-emitter voltage offset are also provided.

Abstract: A power control unit protection apparatus is provided in association with a power control unit for controlling high or low power supply selectively to a loud speaker. The power control unit protection apparatus has an average current detector for detecting an average current supplied to a transformer, a temperature detector detecting the temperature of the transformer, and a timer. When the average current exceeds a predetermined level, and when the temperature rises above a predetermined temperature, timer starts to count a predetermined time. After the count, a cut off signal is produced to cut off the use of the high power supply from the power control unit. Thus, the power control unit protection apparatus prevents breakdown due to overheating of the power control unit including the power supply transformer by limiting the power supplied to the speaker.

Abstract: A self-oscillating DC to DC converter which includes either two or four transistors, three transformers (a converting transformer, a driving transformer and a current transformer) and an inductance.The operating frequency of the converter is fixed by the saturation time of the driving transformer. The base currents of the transistors are mainly supplied by the current transformer so as to be in proportion to the collector currents of the transistors. The operating frequency of the converter is kept constant in spite of load fluctuations. The inductance which is connected in series between a winding of the converting transformer and a winding of the driving transformer. The inductance prevents the two or four transistors from being `on` simultaneously.