Home | Gadget | Fuzzy | Lecturer  | Power  | Transceiver



Find more type here...







High Stability Crystal Time Base


All of the types of oscillators that have been discussed thus far have one inherent problem—their operational frequencies will vary with temperature changes. For digital circuits requiring high-stability oscillators, a crystal-based oscillator is usually employed. Crystals are “piezoelectric” elements with vibrational characteristics that are highly immune to temperature changes. Figure 13-11 is a crystal timebase oscillator.





Depending on the crystal frequency chosen, start with a 10-Mohm resistor for R1, and increase its value as needed. The NTE4011B is a CMOS device, so take precautions in assembly, as detailed previously. Crystal oscillators operate at very high frequencies. To lower the output frequency, an appropriate modulo flip-flop divider circuit is required.