A light emitting device comprises a first light emitting unit and a second light emitting unit connected in series with each other, and a PTF unit connected in parallel with the first light emitting unit and in series with the second light emitting unit. Each of the first light emitting unit and second light emitting unit comprises at least one LED. The PTF unit allows the second light emitting unit to be operated before operation of the first light emitting unit upon application of an AC voltage source. The light emitting device reduces total harmonic distortion and flickering, and improves power factor and optical efficiency. A driving circuit of the light emitting device is also disclosed.