Tektronix 2440, User Manual

Page: 43 / 531

Section 3— 2440 Service
THEORY OF OPERATION
SECTION ORGANIZATION
This section of the manual is divided into three subsec­
tions, with each subsection increasing in detail. The first
subsection is the “Simplified Block Diagram Description”
which contains a general summary of instrument operation
by diagram. A simplified block diagram accompanies the
text. Subsection two is the “Detailed Block Diagram
Description” which discusses the circuit functions in
greater detail and provides a more in-depth look at the
acquisition system. A detailed block diagram is located in
the foldout pages at the rear of this manual. Generally,
both block diagram descriptions follow the signal-flow path
as much as possible and not the schematic diagram
number order as is done in the ‘ Detailed
Circuit Description”.
Subsection three is the “ Detailed Circuit Description”
which discusses the circuitry shown in the schematic
diagram foldouts, also located at the rear of this manual.
The schematic diagram number associated with each
description is identified in the text and is shown on the
block diagrams. For best understanding of the circuit being
described, refer to the appropriate schematic diagram and
the block diagrams. The order of discussion in the circuit
descriptions follows the schematic diagram number order.
INTEGRATED CIRCUIT
DESCRIPTIONS
Digital logic circuits perform most of the functions
within the instrument. Functions and operation of the logic
circuits are shown using logic symbols and terms. Most
logic functions are described using the positive-logic con­
vention. Positive logic is a notation system in which the
more positive of the two logic levels is the HI (or 1) state;
the more negative level is the LO (or 0) state. Voltages
that constitute a HI or a LO state vary between specific
devices. Refer to the device manufacturer’s data book for
specific electrical characteristics or logical operation of
common parts.
The functioning of linear integrated circuit devices in
this section is discussed using waveforms or other tech­
niques such as voltage measurements and simplified
diagrams, where required, to illustrate their operation.
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