1MHz time base without crystal

lektor july/august 1983 23 1MHz time base without crystal Clock generators, for instance, those used in microprocessor systems, are normally crystal controlled. Although crystals have become cheaper over the years, they are stil) expensive items. A ceramic res- onator offers an inexpensive alterna- tive. The sixth significant digit is not often of great importance in a 1 MHz time base, but high frequency stability is. And that is guaranteed by a ceramic resonator (or filter, as it is often called). The circuit shown produces a clock frequency of precisely 1.07 MHz and is eminently Rnt RI. _. Rel Rr2 1N3N 14 5V 0 s ia back to input A, the frequency of the output available at QA is exactly one tenth of the oscillator fre- quency. 1C2 can also be connected as a 5 : 1 divider to give a clock frequency of 2.14 MHz, which may be of interest to Z80 enthusiasts. The circuit also works very well with a 455 kHz ceramic filter. To ensure correct operation of the oscillator at this low freque...