Tektronix 070-8462-03, Instruction Manual

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Theory of Operation
1735 HD High Definition Waveform Monitor
4–15
Horizontal Sync Generator.
The horizontal sync generator produces a pulse that
starts just before sync and ends at the leading edge of sync. Since the 1735 HD is
a multi-standard instrument, the time from the leading edge of sync to the start of
the pulse is programmable and controlled by U33 (Diagram 8). The ramp starts
up at the leading edge of sync. A voltage comparator determines when the
HSYNC pulse starts and the ramp resets.
The ramp generator consists of a current source (Q11), a capacitor (C52), a
transistor (Q14) to discharge the capacitor, and an FET input operational
amplifier (U24A) to provide a low impedance output. U19 is a current output
DAC controlled by the master processor (U33).
U9A, a JK flip-flop, is cleared by the output of comparator U7D. When U9A is
cleared, Q14 saturates and C52 discharges. When C52 is discharged, the
comparator releases U9A Clear, and the flip-flop is ready for a composite sync
clock.
Horizontal Blanking Generator. The horizontal blanking starts before horizontal
sync and ends after horizontal sync. It is used to blank sweep retrace and
switching transients.
Timing
Diagram <9>