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Deflection oscillators. Purpose of oscillator. To generate sawtooth trapezoid of sufficient amplitude to drive the output Support the amplitude amplifier Provides pulses necessary to drive a discharge transistor. Trapezoid Generator.
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Purpose of oscillator • To generate sawtooth trapezoid of sufficient amplitude to drive the output • Support the amplitude amplifier • Provides pulses necessary to drive a discharge transistor
Sawtooth deflection current important characteristics that affect the television picture tube • Amplitude – depends on the time constant of the RC network and the source Voltage (possibly at 20V) • Linearity – can be affected by the constant of the circuit and the total time the capacitor allowed to charge. • Frequency horizontal and vertical sawteeth FCC rules: Black and white at 60 Hz and 59.94 for color.
Transistor Blocking oscillator with its associated waveforms
Common television oscillator in the vertical and horizontal circuit • The blocking oscillator – self activated switch that is closed for a short time, allowing the sawtooth capacitor to charge then it will be open for a long time for trace, permitting capacitor to discharge. • The multivibrator – used in solid state emitter coupled circuits • The overdiriven Hartley oscillator • The IC oscillator