Receiving circuit and electronic apparatus for optical communication

A receiving circuit, for use in an optical communication, from which an output signal is outputted in accordance with a signal optical pulse incident to a light-receiving element, the receiving circuit comprising:

• a variable output circuit for detecting a pulse width of the signal optical pulse, selecting one pulse width from a plurality of pulse widths in accordance with the pulse width thus detected, and outputting an output signal having the one pulse width thus selected;
• the variable output circuit includes a first pulse generating circuit generating a received pulse by comparing an electric signal converted from the signal optical pulse with a threshold, the received pulse being a digital signal;
• wherein either the received pulse generated by the first pulse generating circuit or a pulse having a different pulse width from that of the received pulse is selectively outputted as an output signal, in accordance with the pulse width of the signal optical pulse;
• the variable output circuit includes a second pulse generating circuit for generating a signal having a predetermined pulse width corresponding to a low-speed communication;
• and
• if it is judged that a pulse width of an output from the first pulse generating circuit exceeds a predetermined value, a signal generated by the second pulse generating circuit is outputted as the output signal, instead of outputting the received pulse;
• and
• wherein the first pulse generating circuit includes a one-shot pulse generating circuit that receives the received pulse and maintains the pulse width of the output signal at a constant value.

A receiving circuit, for use in an optical communication, from which an output signal is outputted in accordance with a signal optical pulse incident to a light-receiving element, the receiving circuit comprising:

• a variable output circuit for detecting a pulse width of the signal optical pulse, selecting one pulse width from a plurality of pulse widths in accordance with the pulse width thus detected, and outputting an output signal having the one pulse width thus selected;
• the variable output circuit includes a first pulse generating circuit generating a received pulse by comparing an electric signal converted from the signal optical pulse with a threshold, the received pulse being a digital signal;
• wherein either the received pulse generated by the first pulse generating circuit or a pulse having a different pulse width from that of the received pulse is selectively outputted as an output signal, in accordance with the pulse width of the signal optical pulse;
• the variable output circuit includes a second pulse generating circuit for generating a signal having a predetermined pulse width corresponding to a low-speed communication;
• and
• if it is judged that a pulse width of an output from the first pulse generating circuit exceeds a predetermined value, a signal generated by the second pulse generating circuit is outputted as the output signal, instead of outputting the received pulse;
• and
• wherein the first pulse generating circuit includes a delay circuit to which the received pulse is inputted.

A receiving circuit, for use in an optical communication, from which an output signal is outputted in accordance with a signal optical pulse incident to a light-receiving element,

• the receiving circuit comprising:
• a variable output circuit for detecting a pulse width of the signal optical pulse, determining a pulse width of the output signal in accordance with the pulse width of the signal optical pulse, and outputting the output signal;
• wherein the variable output circuit includes a first pulse generating circuit generating a received pulse by comparing an electric signal converted from the signal optical pulse with a threshold, the received pulse being a digital signal;
• and
• wherein either the received pulse generated by the first pulse generating circuit or a pulse having a different pulse width from that of the received pulse is selectively outputted as an output signal, in accordance with the pulse width of the signal optical pulse;
• wherein the variable output circuit further includes a second pulse generating circuit for generating a signal having a predetermined pulse width corresponding to a low-speed communication;
• and
• if it is judged that a pulse width of an output from the first pulse generating circuit exceeds a predetermined value, a signal generated by the second pulse generating circuit is outputted as the output signal, instead of outputting the received pulse;
• and
• wherein the variable output circuit still further includes a trigger generating circuit for generating a trigger signal when a pulse generating time of the first pulse generating circuit exceeds a first predetermined period, and a timer circuit for generating a pulse having a second predetermined period, in response to the trigger signal from the trigger generating circuit;
• if the timer circuit outputs no pulse, a pulse outputted from the first pulse generating circuit is outputted as the output signal;
• and
• if the timer circuit outputs a pulse, a pulse outputted from the second pulse generating circuit is outputted as the output signal.