CIRCUIT DESCRIPTION

Section 3—475

Introduction

This section of the manual contains a description of the

circuitry used in the 475 Oscilloscope. The description

begins with a discussion of the instrument, using the basic

block diagram shown in Fig. 3-1. Then, each circuit is

described in detail, using detailed block diagrams to show

the interconnections between the stages in each major

circuit and the relationship of the front panel controls to

the individual stages.

A complete block diagram is located in the Diagrams

Section at the back of this manual. This block diagram

shows the overall relationship between all of the circuits.

Complete schematics of each circuit are also given in the

Diagrams Section. Refer to these diagrams throughout the

following circuit description for electrical values and

relationships.

Digital Logic

Digital logic techniques are used to perform many

functions within this instrument. The function and opera

tion of the logic circuits are described using logic sym

bology and terminology. All logic functions are described

using the positive logic convention. Positive logic is a

system of notation where the more positive of two levels

(HI) is called the true or 1 state; the more negative level

(LO) is called the false or 0 state. The HI-LO method of

notation is used in this logic description. The specific

voltages that constitute a HI or LO state vary between

individual devices. Typical HI or LO logic levels are shown

on the diagrams at the rear of this manual.

It should be noted that not all of the integrated circuit

devices in this instrument are digital logic devices. The

function of non-digital devices are described individually,

using operating waveforms or other techniques to illustrate

their function.

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3-1

Fig. 3-1. Basic block diagram of the 475.

Tektronix 475 User Manual

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