Peak-hold circuit and an infrared communication device provided with such a circuit

An infrared communication device capable of time-sharing multi-channel communication, comprising:

• a photoelectric transfer element for photoelectrically transferring a received infrared signal;
• a peak-hold circuit for capturing a peak value of an output from the photoelectric transfer element and for setting a detection level based upon the peak value;
• and
• an output circuit for waveform-shaping an output from the photoelectric transfer element by level-discriminating the output based on the set detection level,
• wherein the peak-hold circuit includes hold means which captures a peak value of an input signal and a reset means which carries out a resetting operation on a holding value of the hold means when it receives a reset signal, wherein the reset means, upon receipt of the reset signal, improves a response speed of the hold means by a predetermined time period by increasing a charging current and a discharging current of the hold means.

An infrared communication device, which is a bidirectional infrared communication device having light receiving and emitting elements that are integral with each other, comprising:

• a time counter which, based on the fact that no level variation takes place in a transmitted signal during a predetermined period, detects completion of the transmitted signal, and allows a receiving device to restore its sensitivity,
• wherein the receiving device includes:a gain-variable amplifier for amplifying a photoelectrically transferred output from the light-receiving element;
• a first peak-hold circuit for carrying out a peak detection using comparatively short time constant so as to set the detection level based upon the output of the amplifier;
• a second peak-hold circuit for carrying out a peak detection using a comparatively long time constant so as to achieve an AGC operation by detecting a noise level of the output of the amplifier and controlling the gain of the amplifier in response to a result of the detection;
• and an output circuit for waveform-shaping by level-discriminating the output of the amplifier by the detection level that has been set by the first peak-hold circuit,
• wherein the time counter carries out a resetting operation on the gain of the amplifier by resetting at least a holding value of the second peak-hold circuit, thereby allowing the sensitivity restoration.

A peak hold circuit, comprising:

• hold means for capturing a peak value of an input signal;
• and
• reset means for, upon receipt of a reset signal, carrying out a resetting operation on a holding value of the hold means, wherein:
• the reset means includes:
• a first constant current circuit for increasing a charging current to a hold capacitor of the hold means;
• a second constant current circuit for increasing a discharging current from the hold capacitor of the hold means;
• and
• first and second switches for, upon receipt of the reset signal, coupling the hold means to the first and second constant current circuits respectively,
• the reset means, upon receipt of the reset signal, resetting the holding value of the hold means without undershoot.