Patent ID: 8311241

Claim:
A microphone circuit for transmitting infrared light in response to frequency modulated signals, the frequency modulated signals corresponding to audio signals received by a microphone coupled to the microphone circuit, the microphone circuit comprising: a current flow path comprising an infrared diode circuit comprising at least two infrared light emitting diodes; the current flow path also comprising a switch responsive to the frequency modulated signals to control the flow of current through the current flow path in response to the frequency modulated signals to thereby control the flow of current through the infrared diode circuit and the emission of infrared light from the infrared diodes so as to correspond to the audio signals; the current flow path further comprising a resistance circuit comprising at least one resistor; a light emitting diode driver circuit coupled to the switch and to the resistance circuit and operable to drive the switch; a voltage source coupled to the infrared diode circuit; and a voltage regulator operable to vary the voltage of the voltage source; the voltage regulator comprising a feedback circuit coupled to the current flow path to provide a feedback signal corresponding to the current in the current flow path, the voltage regulator being operable to vary the voltage of the voltage source to maintain a substantially constant current through the resistance circuit during at least a portion of the time that infrared light is emitted from the infrared diodes of the infrared diode circuit.