Design and applications of semiconductor components in OPU

There are four kinds of semiconductor components in Optical Pickup Units (OPU), i.e. Laser Diode Driver (LDD), Photo Detect IC (PDIC), Front PDIC (FPD) and High Frequency Modulator (HFM). Two types of LDD described are direct-drive LDD and write strategy built-in LDD. A PDIC is a light to electrical energy converting device, which includes photodiodes and transimpedance amplifiers. FPD is a power monitor PDIC. It has some similarity to PDIC but the requirements differ from PDIC. HFM is used during read by impressing a high frequency current on a DC current to drive the laser diode to let it emit a discontinue power signal. This paper gives overview of these four ICs and highlights on key design, application and testing issues.