VERTICAL OSCILLATOR

The vertical oscillator is an injection-locked ramp generator

with automatic level control. The automatic level control

maintains the oscillator output ramp height with changes in

input frequency. The oscillator requires negative-going TTL

level vertical sync pulses, wider than 200 ns, to lock. In the

absence of vertical sync, the oscillator runs at free-run fre-

quency. The vertical output amplitude is controlled by a volt-

age between 0V and 4V on the V Height input with a range

of about 1.8 to 1, and by a voltage between 3V and 4V on the

Vertical Dynamic Height input with a range of about 1.3 to 1.

The control bandwidth of the V Height input is low due to the

automatic level control, but that of the Vertical Dynamic

Height is greater than 125 kHz. The oscillator has a circuit,

requiring an external capacitor, 2f Cap, that prevents the os-

cillator from locking at twice the vertical sync frequency. The

oscillator ramp voltage is converted into differential currents

superimposed on DC currents of about 315 µA for each out-

put. The voltage to current conversion gain is inversely pro-

portional to the value of the resistor connected between the

Rvert pins (21 and 22). Differential current outputs are pro-

vided instead of voltage to avoid ground noise. The ramp

voltage goes to the parabolic function generator and to two

multipliers used as voltage controlled amplifiers, one for hori-

zontal trapezoid correction and the other for horizontal paral-

lelogram correction.

PARABOLIC FUNCTION GENERATOR

The parabolic function generator makes a parabolic wave-

form from the vertical ramp. Its output goes to three multipli-

ers used as voltage controlled amplifiers, one each for V Dyn

Focus, E-W Pin, and H Bow.

VOLTAGE CONTROLLED AMPLIFIERS

The V Dyn Focus voltage controlled amplifier is controlled by

the V Dyn Focus Cntl input. Its output goes to an op amp

whose output is V Dyn Focus. The voltage controlled ampli-

fier has zero gain at approx. 2V input, maximum positive

gain at 4V, and maximum negative gain at 0V. The E-W Pin,

H Bow, H Trap and H Para voltage controlled amplifiers are

identical to the V Dyn Focus stage, each adjusted by its cor-

responding Cntl input. The bandwidth of the Cntl inputs is

greater than 125 kHz. The E-W Pin and H Bow amplifiers

have the parabolic waveform as their input, and the H Trap

and H Para amplifiers have the vertical ramp as their input.

The parabolic waveform and the ramp amplitudes track the

vertical output amplitude so the correction amplitudes follow

accordingly. The outputs of the E-W Pin amplifier (parabola)

and the H Trap amplifier (ramp) are summed together in an

Pin. The output of the summing amplifier is H Dyn Width,

used for correcting E-W pincushion and horizontal trapezoid

distortion. The outputs of the H Bow amplifier (parabola) and

the H Para amplifier (ramp) are summed together similarly,

with H Bow and H Para equally weighted. The output of the

summing amplifier is H Dyn Cntr, used for correcting hori-

zontal bow and horizontal parallelogram distortion. All three

op amp outputs are identical structures and are typical low

output impedance type op amp outputs, capable of sinking

or sourcing 5 mA minimum.

Block Diagram

DS012324-3

FIGURE 3.

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