With the advent of high speed HCMOS circuits, it is possible to build systems with clock rates of greater than 30 MHz. The familiar gate oscillator circuits used at low frequencies work well at higher frequencies and either LC or crystal resonators maybe used depending on the stability required. Above 20 MHz, it becomes expensive to fabricate fundamental mode crystals, so overtone modes are used.

This article explains the specifications and characteristics of crystals and crystal oscillators, and aids in specifying crystals and working with crystal vendors. The article covers the significant performance characteristics of crystals, which include resonance frequency, resonance mode, load capacitance, series resistance, holder capacitance, motional inductance and capacitance, temperature calibration, and drive level.

On following pages circuits are shown for 3rd overtone crystals 15 to 65MHz and 5th overtone crystals 60 to 105 MHz operating in their series resonant mode. In both of these circuits with the crystal short circuited, the oscillator should operate at or near the required frequency. With the crystal in circuit L1 should be adjusted for either (a) minimum voltage across the crystal or (b) for the exact frequency required. Ideally, these two points would coincide but they rarely will due to the need for a manufacturing tolerance on crystal frequency. If L1 is of incorrect size it is possible for the oscillator to operate on a different order of overtone, for this reason it is important to accurately check the output frequency.

A variable oscillator covers 3.2 to 22 MHz in two bands—providing coverage of 80 through 15 meters plus most crystal-filter frequencies. Optional 455 kHz and 10.7 MHz crystal oscillators can be switched on-line for precise if alignment. Generator output is on the order of 4 volts p-p into a 500 ohm load.

The swept-frequency oscillator offers an inexpensive source of discrete frequencies for use in testing digital circuits. In this configuration, the circuit generates an 80-second seguence of eight frequencies, dwelling for 10 seconds on each frequency. You can change the dwell time or the number of frequencies. Frequencies can range from 0.005 Hz to 1 MHz. The programmable crystal oscillators, PXOs, IC2 and IC4 can each generate 57 frequencies in response to an 8-bit external code.

Before the advent of broadband communications receivers with synthesized oscillators, high-grade, hamband receivers used crystal oscillators and a variable IF to cover relatively narrow (500-600 kHz) frequency segments. The schematic shows a circuit that will adapt most of these receivers to cover the long-wave (150-400 kHz), standard (520-1600 kH

A microcontroller (MCU) is a small computer in a single integrated circuit consisting of a CPU is relatively simple combined with support functions such as crystal oscillators, timers, sensors, serial and analog I / O etc. Microcontroller designed for small applications. Thus, in contrast to microprocessors used in personal computers and high perf

Understanding how quartz-crystal resonators operate can lead to designing crystal oscillators with improved stability and better noise performance..

Although there are many different configurations for Crystal Oscillators, the most common are the discrete and integrated circuits Pierce and environment RLC Bridge. When needed very good frequency stability and reasonably simple circuits, the discrete Pierce is a good choice. When your main concern is the low cost and

In crystal oscillators, the usual electrical resonant circuit is replaced by a mechanically vi ­brating crystal. The crystal (usually quartz) has a high degree of stability in holding con ­stant at whatever frequency the crystal is originally cut to operate. The crystal oscillators are, therefore, used whenever great stability is needed, for examp

Power circuit Reset circuit USB connection ABDAC sound DAC Interface JTAG and Nexus debug ports Clocks and crystal Oscillators 1 Introduction A good hardware design comes from a proper schematic. Since UC3B devices have a fair number of pins and functions, the schematic for these devices CAN be large and quite complex. This application note d

The RF2516 is a monolithic integrated circuit intended for use as a low-cost AM/ASK transmitter. The device is pro- vided in a 16-pin QSOP-16 package and is designed to provide a phased locked frequency source for use in local Oscillator or transmitter applications. By RF Micro Devices

The circuit is presented as a starting point - there will be some experimentation needed for each individual case. For the popular microwave bands the LOs are usually generated from overtone crystal oscillators followed by multipliers, with the following table showing the usual LO frequencies for the narrowband segments along with the associated crystal frequency. The final

The schematic above illustrates dividing a crystal oscillator signal by the crystal frequency to obtain an accurate (0. 01%) 1 second time base. Two cascaded 12 stage counters (CD4040) form a 24 stage binary counter and the appropriate bits are gated together to produce the desired division. Using a crystal of some even multiple of 2 is desirable so that one stage

The circuit is only suitable for fundamental crystals as there are no mode suppression components. The oscillator transistor Q104 is cutoff most of the time except for a short period at the peak of the crystal current waveform. Q103 regulates the dc collector current of the oscillator transistor Q103. The dc collector current of Q104 and hence the

In Figure 7-2 is the FSK signal demodulation circuit composed of the digital phase-lock. The circuit consists of 2 oscillators with different frequencies, i.e crystal oscillators X (the frequency is 983.04KHz) and X2 (the frequency is 1.2288MHz) compose the oscillator, and X2 consists of the frequency converting circuit 74HC157, frequency splitting circuit..

Crystal oscillators are those in which a specially-cut crystal controls the frequency. CRYSTAL-CONTROLLED OSCILLATORS are the standard means used for maintaining the frequency of radio transmitting stations within their assigned frequency limits. A crystal-controlled oscillator is usually used to produce an output which is highly stable and at a v