Tickler oscillator circuit

  
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When the circuit is first powered up, neither transistor will be switched on. However, this means that at this stage they will both have high base voltages and therefore a tendency to switch on, and inevitable slight asymmetries will mean that one of the transistors is first to switch on. This will quickly put the circuit into one of the above sta
Tickler oscillator circuit - schematic

tes, and oscillation will ensue. Very roughly, the duration of state 1 (high output) will be related to the time constant R2. C1 as it depends on the charging of C1, and the duration of state 2 (low output) will be related to the time constant R3. C2 as it depends on the charging of C2 ” and these time constants need not be the same, so a custom duty cycle can be achieved. However, the duration of each state also depends on the initial state of charge of the capacitor in question, and this in turn will depend on the amount of discharge during the previous state, which will also depend on the resistors used during discharge (R1 and R4) and also on the duration of the previous state, etc. The result is that when first powered up, the period will be quite long as the capacitors are initially fully discharged, but the period will quickly shorten and stabilize. An odd number of inverters are required. Using a minimal number of stages within the oscillator allows for maximum frequencies to be achieved, however this will be sensitive to voltage variations. By using a larger number of stages, the noise, due to voltage variation is minimised. The frequency is not exact due to variations in transition time. This is compensated for by controlling the current passing through the transistors. This also allows you to make it a Voltage controlled oscillator (VCO). OCXO (short for Oven Controlled X-tal (Crystal) Oscillator) is a technique...



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