The LP oscillator
The LP, or low power oscillator, is designed to trade
speed for low power operation. Although this circuit
shares the same topology (schematic) as the XT
oscillator, the transistors used in the LP oscillator have
a higher Rdss value and draw considerably less
current. This configuration is optimum for low frequency
operation, because it trades the away unnecessary
high frequency responses for dramatically reduced
operating currents.
The XT oscillator
The XT oscillator is designed to give a compromise
between high frequency performance and modest
power consumption. The gain of this oscillator is as
much as 15 times higher than the LP oscillator. This
middle range will be used for frequencies up to 4 MHz.
The HS oscillator
The HS oscillator is designed to give the maximum gain
and frequency response. The current consumption is
accordingly higher. The gain is roughly five times higher
than that of the XT oscillator. This gives the PICmicro
the ability to operate at frequencies up to 20 MHz.