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Pin Photodiode for Optical Communication Applications

IP.com Disclosure Number: IPCOM000050964D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Balliet, L: AUTHOR [+2]

Abstract

Fig. 1 shows a light receiving/transducing circuit, for converting light signals into corresponding electrical output signals, which uses a PIN photodiode of the form shown in Fig. 2 in association with a feedback resistor R(f). The predominant noise source in this circuit is the feed-back resistor. A less "noisy" circuit arrangement is shown in Fig. 4. This circuit arrangement uses the modified PIN photodiode structure shown in Fig. 3.

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Pin Photodiode for Optical Communication Applications

Fig. 1 shows a light receiving/transducing circuit, for converting light signals into corresponding electrical output signals, which uses a PIN photodiode of the form shown in Fig. 2 in association with a feedback resistor R(f). The predominant noise source in this circuit is the feed-back resistor. A less "noisy" circuit arrangement is shown in Fig. 4. This circuit arrangement uses the modified PIN photodiode structure shown in Fig. 3.

The modified photodiode structure is produced by the same process as the basic photodiode structure of Fig. 2, but differs in that it contains a split cathode which effectively forms two separate diode structures. The separate cathode portions may be designed on a customized basis with different areas, as suggested in Fig. 3, for specific circuit applications, including the specific application suggested in Fig. 4. In Fig. 4, one of the diode sections 4 is connected to a positive potential in conventional fashion, forming the equivalent of the diode circuit shown in Fig. 1, and the other sections replaces the feedback resistor R(f) in the circuit configuration of Fig. 1. By appropriate construction and sizing of the other section, the feedback path may be tailored for the desired performance. The feedback path, as shown, produces less noise. Additional feedback can be provided by introducing capacitance in parallel with the feedback diode section.

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