Tektronix 2215, Instruction Manual

Page: 90 / 345

The nonlinear current is connected to the em itters o f
the diffe re n tia l am plifier composed o f Q811 and Q812.
The em itters o f the tw o a m p lifie r transistors are held at a
constant voltage by the action o f Q813. A U T O IN T E N ­
S ITY co n tro l R807 is connected to the base o f Q811 via
R 811. It controls the p o rtio n o f the boost current th a t goes
to the summing ju n ctio n o f U835B. Boost current is pro­
portional to the true beam current required at the faceplate
o f the crt.
The c rt trio d e compensation c irc u it is an inverting
operational am p lifie r w ith nonlinear feedback. It is
composed o f U835B, R834, R835, C834, and CR834.
O u tp u t voltage o f the c irc u it changes in response to the
in p u t current in a manner th a t complements the nonlinear
trio d e characteristics o f the crt. This o u tp u t voltage is
applied both to the Intens Level signal line and to the
Z-A xis A m p lifie r via the A and B Z-A xis Logic Switching
circuits. The Intens Level signal is also applied to the Focus
c irc u it (Diagram 9) fo r use in focus tracking o f the intensity
level changes.
The intensity o f the display is allowed to reduce to zero
through the action o f CR809, VR 809, and R809. W ith o u t
this circu it, the A u to Intensity c irc u it w o u ld not allow the
intensity to go to zero when the A U T O IN T E N S IT Y
co n tro l is set to m inim um intensity.
Z-Axis Amplifier
The Z-A xis A m p lifie r controls the c rt intensity level
via several input-signal sources. The e ffe ct o f these in p u t
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