Abstract: In a circuit for detecting a recorded area of an optical disk, when unnecessary noise is superimposed on the space portion of the digitized signal (RF) of an RF signal from the optical disk, a counter (20) for detecting a space portion detects the noise and resets a counter (81) for detecting a recorded area with an output signal S21 therefrom. This prevents the counter (81) for detecting a recorded area from erroneously outputting a recorded area detection signal (S12) due to the noise. As a result, a counter (80) for detecting an unrecorded area outputs an unrecorded area detection signal (S20) with high accuracy to bring a recorded area signal (RECD) from a flip-flop circuit (82) to the L level. Accordingly, an unrecorded area can be detected as it is inherently with high accuracy without being erroneously recognized as a portion in which a mark portion has been recorded.

Abstract: In a circuit for detecting a recorded area of an optical disk, when unnecessary noise is superimposed on the space portion of the digitized signal (RF) of an RF signal from the optical disk, a counter (20) for detecting a space portion detects the noise and resets a counter (81) for detecting a recorded area with an output signal S21 therefrom. This prevents the counter (81) for detecting a recorded area from erroneously outputting a recorded area detection signal (S12) due to the noise. As a result, a counter (80) for detecting an unrecorded area outputs an unrecorded area detection signal (S20) with high accuracy to bring a recorded area signal (RECD) from a flip-flop circuit (82) to the L level. Accordingly, an unrecorded area can be detected as it is inherently with high accuracy without being erroneously recognized as a portion in which a mark portion has been recorded.

Abstract: The laser drive device of this invention includes a laser, first and second current sources, a current amplifier, and first and second transistors. When the first transistor is OFF, a first current from the first current source is supplied to the current amplifier, where the current is amplified to generate a laser current to be supplied to the laser. Thus, the laser is turned ON. During this time, the second transistor is ON, allowing a second current to flow from a power supply node into the second current source. When the first transistor is ON, the entire or part of the first current flows into the second current source through the first transistor. This reduces the current supplied to the current amplifier and thus the laser current, resulting in turning OFF the laser. During this time, the second transistor is OFF. The values of the first and second currents are determined by a set current value.

Abstract: The laser drive device of this invention includes a laser, first and second current sources, a current amplifier, and first and second transistors. When the first transistor is OFF, a first current from the first current source is supplied to the current amplifier, where the current is amplified to generate a laser current to be supplied to the laser. Thus, the laser is turned ON. During this time, the second transistor is ON, allowing a second current to flow from a power supply node into the second current source. When the first transistor is ON, the entire or part of the first current flows into the second current source through the first transistor. This reduces the current supplied to the current amplifier and thus the laser current, resulting in turning OFF the laser. During this time, the second transistor is OFF. The values of the first and second currents are determined by a set current value.

Abstract: The laser drive device of this invention includes a laser, first and second current sources, a current amplifier, and first and second transistors. When the first transistor is OFF, a first current from the first current source is supplied to the current amplifier, where the current is amplified to generate a laser current to be supplied to the laser. Thus, the laser is turned ON. During this time, the second transistor is ON, allowing a second current to flow from a power supply node into the second current source. When the first transistor is ON, the entire or part of the first current flows into the second current source through the first transistor. This reduces the current supplied to the current amplifier and thus the laser current, resulting in turning OFF the laser. During this time, the second transistor is OFF. The values of the first and second currents are determined by a set current value.

Abstract: In an optical disc apparatus, a semiconductor SLD driving device is mounted on an optical pickup in order to realize a high speed switching of drive current for a semiconductor laser diode (SLD), necessary for recording data. The SLD is placed. within 5 cm from the SLD driving device. The driving device becomes a heat source due to driving current of the SLD, and increases a temperature of the optical pickup. Since the temperature rises proportionally to power consumption, power saving is required. A voltage supplied to the driving device is controlled to be a minimum level necessary for keeping the driving device still working on basic functions. The SLD driving device is mounted to the optical pickup, and this driving device handles N pieces of input signals for setting semiconductor laser power and N pieces of switch-timing-input-signals for selecting respective input signals.