Crystal Oscillator Application Notes | ||||
Crystal oscillator is the most common type of oscillator used and has applications in virtually every aspect of the electronics industry. The crystal oscillator is used to establish a reference frequency used for timing purpose. | ||||
Crystal oscillator typically consists of an amplifier and a feedback network that selects a part of the amplifier output and returns it to the amplifier input. A simplified block diagram of such a circuit is shown below in (Fig.1). | ||||
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The basic criteria for oscillation in an oscillator are: | ||||
1. The open loop gain must be greater than the losses around the oscillator loop and 2. The phase shift around the oscillator loop must be either 0 or 360 degrees. |
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An oscillator can be used to generate different type of waveforms. The most common types of waveforms produced by an oscillator are sinusoidal and square. | ||||
The main parameters used in specifying a clock oscillator are listed below. | ||||
Logic TTL, HCMOS | ||||
In general, an HCMOS oscillator will drive TTL circuitry (not vice versa). The industry is moving away from the TTL logic as IC manufacturers are discontinuing the supply of many common TTL ICs. | ||||
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