BENDIX/KING KX 165A
Rev 0, Jun/2000 15610M00.RCD Page 4-45
are driven differentially by two buffer amplifiers U4 and U6. The maximum differential voltage is
set by D-Bar slope adjust digital pot U1-B. Voltage reference IC U5 outputs a fixed 2.5 Vdc. R4
and R3 divides this to 1.25 V that is applied to the non-inverting input of OP-Amp U6. The output
of this circuit is the Voltage Reference board output. This output drives the +LEFT D-Bar output.
The fixed 2.5Vdc output from U5 is also connected to the voltage divider formed by R15, U1-A,
and R14. The wiper of U1-A this applied to the non-inverting input of U4. The output from U4
drives the +RIGHT D-Bar output.
4.3.8.3 TO/FROM driver
The +TO and +FROM outputs are driven to produce a differential output pair. Logic levels are
translated into a positive difference voltage +TO relative to +FROM for “TO” indication and a neg-
ative voltage +TO relative to +FROM for “FROM” indication. Q3 and Q1 form the +TO driver, while
Q4 and Q2 form the +FROM driver.
4.3.8.4 Flag driver
The +FLAG output is driven by a buffer amplifier U7 with an output resistance a 1.5 kOhm. A logic
level from the main board drives the input of this buffer. The -Flag output is connected to unit
ground. A high logic input produces a more positive output voltage to generate a “Hidden Flag”
indication.
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