A circuit in a mobile terminal for measuring heartbeat/stress. The circuit includes a photoplethysmography (PPG) sensor having first and second green light-emitting diodes (LEDs) first and second LED drivers respectively connected to the first and second green LEDS and respectively configured to drive the first and second green LEDs and a processor configured to control the first and second LED drivers to alternately turn on the first and second green LEDs within one driving period to respectively produce first and second PPG signals, and measure a users heartbeat/stress using the first and second PPG signals that have a corresponding signal quality equal to or greater than a predetermined threshold.
