Output Amplifier - Tektronix 7B92A Instruction Manual

Theory of Operation--7B92A
NOTE
The positioning offset voltage and the selected sweep
ramp are connected to 0942 and 0952 . The push-pull
When operating in the Intensified mode, the inten-
output is connected to the oscilloscope mainframe
sified zone is controlled by the intensity of the test
through pins A11 and B11 .
oscilloscope instead of the 7892A CONTRAST and
INTENSITY controls.
Sweep Display. The Sweep Display flip-flop, U856A,
determines which sweep ramp is displayed. When the time
base is in the Normal or Delayed Sweep mode, S800
connects R861 and R862 to ground . With the Set input of
U856A low, pin 5 is held high and pin 6 is held low. The
high level on pin 5 of U856A inhibits the Delaying Sweep
signal at the Output Amplifier. The low on pin 6 allows the
Delayed Sweep signal to be coupled through the Output
Amplifier to the oscilloscope mainframe.
If the time base is in the Alternate mode, the Set, J, and
K inputs of U856A are all high . The end of each Aux. Gate
pulse toggles U856A, which allows alternate display of the
Delaying and Delayed Sweep ramps.
When the time base is in the Intensified Sweep mode,
pin 15 of U856A is held low by pin 4 of 0635, clearing flip-
flop U856 . With pin 5 of U856A low, the Delaying Sweep
signal is coupled to the output amplifier.
Output Amplifier
'rhe Output Amplifier connects the sweep signal to the
oscilloscope mainframe and provides an offset voltage to
position the trace on the graticule.
The Delaying Sweep and Delayed Sweep ramps are
connected to 0900 and 0910, respectively . The Delaying
Sweep Inhibit and Delayed Sweep Inhibit signals saturate
either 0902 or 0912 to prevent that sweep ramp from
being amplified and coupled to the oscilloscope main-
frame .
The Auxiliary Sweep Amplifier, 0456 and 0458, is a
unity-gain amplifier that couples the Delaying Sweep
ramp to the mainframe. This signal may be connected to
the -f- Sawtooth output of the oscilloscope mainframe.
Readout
O8
The oscilloscope readout system in 7000-Series
Oscilloscopes provides alphanumeric display of informa-
tion encoded by the plug-in units. This display is
presented on the crt on a time-shared basis with the
waveform display.
The oscilloscope readout system produces a pulse
train consisting of 10 negative-going pulses called time-
slots. Each pulse represents a possible character in a
readout word, and is assigned a time-slot number cor-
responding to its position in the word . Each time-slot
pulse is directed to 1 of 101ines, labeled TS-1 through TS-
10 (time slots 1 through 10), which are connected to the
vertical and horizontal plug-in compartments. Twooutput
lines, row and column, are connected from each channel
(two channels per plug-in compartment) back to the
oscilloscope readout system .
Data is encoded on the output lines either by connec-
ting resistors between the output lines and the time-slot
input lines, or by generating equivalent currents . The
resultant output is a sequence of analog current levels on
the row and column output lines. The row and column
current levels address a character matrix during each
time-slot ; thus, selecting a character to be displayed or a
special instruction to be followed .
The POSITION control, R930, offsets the ramp
waveform to horizontally position the displayed trace.
Transistors 0926 and 0932 turn on when contact 52 is The encoding resistors are selected by the TIME/DIV
closed and the Delaying Sweep Inhibit signal is high . OR DLY TIME and DLY'D Time/Division switches . Table
These transistors provide additional offset at fast sweep
3-1 lists the resistors that control the readout characters
rates.
and functions.