Tektronix TEKFAX ADA400A, Instruction Manual

Page: 68 / 80

Maintenance
56
ADA400A Differential Preamplifier
Replacement Parts
Refer to the Replaceable Parts section beginning on page 59 for a list of
customer replacement parts.
Theory of Operation
Figure 21 illustrates the functional blocks of circuitry from left to right in the
order of input to output. The darker boxes in the illustration designate front panel
controls and lines with arrows indicate the functional blocks that the controls
affect.
1 M /
1 Ω
Select
High-Z
Attenuator
(1/1, 1/100)
Input Coupling/
Input Protection
Scale Factor
Coding
Signal Out
+5V
Ground
Output
Cable
TEKPROBE
Interface
Oscilloscope
+15V
--15V
Overrange
Detect
+
--
DC
Offset
+
+
--
Low-Pass
Filter
Input Coupling/
Input Protection
High-Impedance
Amplifier
AC-GND-DC
Low-Z
Attenuator
(1/1, 1/10)
Gain .1, 1, 10, 100
ADA400A Differential Preamplifier
Upper Bandwidth Select
100 Hz, 3 kHz, 100 kHz 1 MHz
On/Off,
Coarse, Fine
Output
Amplifier
Input
Data
50
Ω
Gain = X10
Gain = X10
AC-GND-DC
Figure 21: Diagram of the ADA400A Differential Preamplifier