SMD Crystal Oscillators

A Surface Mount Device (SMD) is any device that is packaged in a way that allows the leads to be soldered directly onto the pads on the surface of a circuit board.  This is in contrast to a through hole (TH) device where the leads are threaded through holes in the board and then soldered to pads on the opposite side of the circuit board.  A crystal oscillator is a device that relies on the piezoelectric and resonant properties of crystals to generate an electrical signal that repeats at a precise frequency.  Applying an electrical potential to a crystal causes electrical stress that induces a brief vibration.  Sustained resonance can be obtained by amplifying the resulting electrical signal and feeding it back into the crystal.  This process results in an electrical oscillator that is extremely stable and temperature independent.