Tektronix CURVE-TRACER 576 Instruction Manual page 73

I
I
I
I
I
I
I
l
......
I
I
I
I
I
I
l
a'-'
l
High Impedance
Input
Low Impedance
Input
+
+
03
+
Ru
Deflection
Plates
Rs
+
Substitutions from Display
Amplifier Schematic
+
Circuit Description-Type 576
+
I L1 conducted by R L 1
IL2 conducted by RL2
I D conducted by R D
018
High Impedance
028
Low Impedance
Input
Input
Vertical Simplified Horizontal
Amplifier
Schematic Amplifier
0531A & 8 01A & 8 0631A & 8
0533A & 8
02A & 8 0633A & 8
0560 03 0660
0569
04 0669
0578
05
0678
0587 06 0687
Fig. 3-12. Simplified schematic of display amplifier.
impedance inputs are equal (Is= 0) and that the positioning
currents are unequal (lp1
=I=
lp2). From Equation 3-1 the
load currents are found to be:
I L 1
=
I P1 - I D (Equation 3-3)
IL2
=
lp2 -lo (Equation 3-4)
By subtracting Equation 3-4 from Equation 3-3, it is
shown that the difference in the two load currents exactly
equal the difference in the two positioning currents_
©
IL1 -IL2
=
lp1 -IP2 (Equation 3-5)
Since the positioning currents are now unequal, the load
currents (I L 1 and I L2) are unequal, which again changes the
voltage potential between the deflection plates of the CRT_
These two examples have shown that the voltage be-
tween the deflection plates (and thus the position of the
electron beam as it strikes the face of the CRT) is con-
trolled by two means, the voltage applied to the high
impedance inputs and the positioning currents applied to
3-19