Tektronix 2215 Instruction Manual page 91

response n m e . r u r negative ucm sm uns ui m e
as well as fo r dc and low-frequency signal components,
Q847 acts as the am plifier, w ith
current.
Diode CR856 prevents the Z-A xis o u tp u t signal from
going negative, and neon lamps DS854 and DS856 provide
protection to the Z-Axis A m p lifie r in the event o f high-
voltage arcing in the crt.
The am plifier gain w ith respect to the A o r B Z-Drive
current is set to about 10 by the negative feedback supplied
from the collectors o f Q847 and Q850 to the base o f Q845
via feedback resistor R846. The gain w ith respect to the
external Z-Axis Input signal is held to about three by R801,
R802, and R803 in series w ith the external in p u t signal.
Diodes CR801 and CR802 provide protection fo r the
Z-Axis A m p lifie r in case o f an accidental application o f
excessive signal am plitude to the Z -A X IS INPUT connector.
When CHOP V E R T IC A L MODE is selected, the Chop
Blank signal is applied to the co lle cto r o f Q841 during the
display switching tim e. Signal c u rre n t is shunted away from
CR844, and the forw ard bias o f Q844 increases to the
blanking level. When blanked, the o u tp u t o f the Z-Axis
A m p lifie r drops to about +10 V , and the c rt beam current
is reduced to below viewing intensity to elim inate chop
switching transients from the display.
For an X-Y display, the A Z-Drive and B Z-Drive signal
currents are switched o ff. When the X Y signal is LO,
CR837 is forw ard biased and Intens Level current flow s
biynai,
Q850 supplying the
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