An LED lamp module designed to be easily retrofitted into existing incandescent based light fixtures with minimum modification is provided. The LED lamp module includes a generally circular metal core board including a first surface and a second surface; at least one LED disposed centrally on the first surface of the metal core board; and a flat annular printed circuit board including a current driver circuit for powering the at least one LED, the annular printed circuit board being disposed around the at least one LED and electrically coupled to the at least one LED, wherein the second surface of the metal core board is configured to contact a host fixture and heat generated by the at least one LED is conducted to the host fixture. The LED lamp module uses the host light fixture as a heat sink to transfer and dissipate heat to the external environment.