Tektronix 5A26 User manual

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T EK T R O N IX
1
1
1
1
1
Te k tronix, Inc .
Ρ . Ο . Box500
Beaverton, O r egon 97077
ι
ο7 α - ιο 47- οο
I N
ST R UCTIO N M A NU A L
Serial Number
F irst P ri n ting JUNE 1975

WARRANTY
All TEKTRONIX instruments
are
w
arrantedagainst
detectivematerials and wor km an shi p for one y ear .
A ny
q u estions
w ith r
espect to' the w arra n t y s h o u ld
betaken up with your TEKTRONIX Field En gi neer - or
representative .
All re qu ests for repairs and replacement parts
sh o u ld b e directed to the TEKTRONIX F iel d Office
or representative in your
area . This
ωίΗassu
re you
t h e fastest possible service . P lease include
instrument
Type
N u mber
o
r P art
Number and Ser
Number w ith all re qu ests fo r parts or ser u ί r e .
Specifications and price change privileges reserved
.
Co p yrig
h
t ,
1975 by Te k tro n ix, Inc ., B eaverto n ,
Oregon . P rinte
d
i n
t he U n ited States of A m erica . All
rig h ts reserved . Contents
of
t h
is p ublicatio
n
m ay not
be re p roduce d i n any fo r m w it hou t p
er
m ission
of
Te k troni x , Inc .
U .S .A .
and
foreig n
T E
KTR ON IX products co vered
by U .S . a nd foreig n paten
ts and/or
pate
n
ts
pe ndi
n g .
T EK TR ON IX is α registere d trademar k
of Tektronix,
Inc .

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TA BLE O F CO N T ENTS
P AG Ε

P AG Ε
LIST O
F
ILLUSTRATIONS

i

S E CTIO N 2 T HE O R YO F O PER ATIO N
L IST
O
F TA BLE S

i

BL OC K DIAG R A M DE SC R I P TIO N 2-1
S E CTIO N 1 O PER ATI NG I N ST RU CTIO N S

CI R CU IT O PER ATIO N 2-2
PREP A R ATIO N F O RU SE

1-1

PRE A MPL I F I ER

2-2
CO N T R O L S, CO NNECTO R S, A ND

1-1

OU T PU T A MPL I F I ER S

2-3
I N DICATO RS

RE ADO U T

2-5
B ASIC O PER ATIO N 1-3
P re p aration

1-3

S
E
CTIO N 3 REPL AC E A BLEELE
CT R ICA L P A R TS
Ste p Attenuator B alance Ad j ustme n t

1-3
Gain
C
h ec k 1-4

S E
CTIO N 4 S ERV ICE I NF
O RM ATIO N
DE
TAI
LE D O
PER ATI N
G
I NF
O RM
ATIO N 1-4

S ERV IC ES A V AI L A BLE

4-1
Applying
Signals

1-4

M
AI N T EN A NC E 4-1
P re-C h arging

1-4

Circ u
it
B
oar d
R emoval

4-1
Sig n
al
In p
ut Connectors

1-4

AD JU ST MEN TS A F T ER
REP AI R

4-1
H ig h Im ped ance In p u t

1-5

DIAG R AM S

4-2
Dis p lay P olarity

1-5

BL OC K DIAG R A M
Deflection F actor

1-5

AD
JUST
MEN T PR
OC
E
D URE
V oltage Comparison M eas urements

1-5

P A R T L OCATIO NS
A
N
D DIAG R AM S
Diffe r en tial
O p
eration

1-5
V oltage
Pr
obes

1-6

S E CTIO N 5 REPL
AC
E A BLE
ME CH AN ICA LP AR TS
Differential M
easurements

1-6
S PE CI F ICATIO N S

1-7

C
H
A
N
G E I NF O RM ATIO N
LIST OF ILLUSTRATIONS
FIG URE

FIG URE
NO .

P AG E NO .
1-1

5 Α 26 Du al Differential Am p lifier .

ii

4-3

A dju stment locations .
1-2

Front-panel cont r ols, conn ectors an d 1-2

4-4

Α 1, A2-Channel 1
and 2
Pr
eam p
lifier circuit
i nd icators .

b
oar d component an d test p oint locations .
1-3

Dimensions .

1-9

4-5

Α 2, A2-Channel 1 a nd2P reamplifier circuit
2-1

F
loating
P
ower Su pp ly d etaile d bloc k 2-4

boar d locatio n s .
d iagram s h owing sta n d i ng cu r re n t p at h s

4-6

A3-Main
circuit boa r d com po n e n t a n d test
t hrough t he P ream p lifie r .

p oint locatio n s .
T he ill u
strations in Section 4 are locate don fol dout pages

4-7

A3-Main ci r c u it b oar d locatio n .
at th e back of the ma n ual .

4-8

A3-Main circ u it b oar d component locations .
4

4-9

A3-Main circuit board location .
-1

Circ u it b oar d locations .
4-2

Common-mode re j ectio n (cm r ) display .
L IST O F TA
BLES
TA BLE
NO .

P AG Ε
1-1

E lectrical Sp ecifications

1-7
1-2

E nvironmental S p ecifications

1-8
1-3

Ph ysical Specifications

1-8
5 Α 26

Fig . 1-1 .
5
Α 26
Dual Differential Amplifier
.

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T he 5 Α 26 Dual Differe n tial Am p lifier is α d ual-trace h ig h -gain d ifferential amplifier plug-in for u se wit
hTe k tronix 5000 Series
Oscilloscopes . T h e unit contains two i d entical in d e p en dent am p lifier chann els t h at feature h ig h sensitivity an
dα h ig h common-
mo d e re j ectio n ratio .
E
achch a
n nel h
as α
ban dwid t h capability of do to 1 mega h ertz, an dα front- p anel pu s h button switch allows the re d uction of
t
he
up p
er b
an d widt
h limit, t hu s increasing t h e signal-to- n oise ratio for low freq u ency applications . E it h er chann el may be
used
for single
c
h annel d isplays, or electronically switche d to p ro d uce dual-trace dis p lays .
An
ill u minate d k no bsk irt provi d es α d eflectio nfactor rea dout, w h ic h is also d isplayed on t h e crt w h en used i nan oscillosco p
e
with rea dou t cap abilities .
PREP A R ATIO N
F
OR US
E

4

V
O
L
TS/DI
V Switc h
es-
V olts per ma j or graticule
Ο
d ivisio n . Selects calibrate dd eflection factors from
'

T he
5
Α
26
is cali b rate d an d ready for use w h en receive d .

50 microvolts/ d ivision to 5 volts/division ; 16 steps
in
T he unit may be installed in any p l u g-in com p artment . R e-

α 1-2-5 se q uence . Kn ob s k irt is illuminate
dto in d i-
fer to t he oscilloscope instruction man u al for information

cate d eflection factor, and 10
Χ scaling
of
bot h k no b
on Χ - Υ operation . To install, align t he u pp er an d lower

s k irt and
crt rea
d
out
is
provi de
d
automatically w h en
grooves of t h e 5 Α 26 with t he plug-in compartment track s,

α 10
Χ
co
d e dp robe is used .
an d fully i n sert t he 5 Α 26 u n til it loc k s i nto place . To
re-
move,
pull
the release latc hto disengage t h e 5 Α 26 from t he
' ~ oscillosco p e . CA L ( V aria b le V O L TS/DI V ) Controls-
P rovi d es υη -
calibrated continuously varia b le d eflection
factors
between t he cali b rate d settings of
t he VO L TS/DI V
CO N T R O L S, CO NNE CTO R S, A N D I N DICATO
R
S

switc
h
and
exten d
st
h e d eflection-factor range to
12 .5
volts/
d ivision .
T he following descri b es t h e
f
u nction of t h e front- p anel
controls, con n ectors, an d indicators . R
efer
to
F ig . 1-2
for
t he locatio nof t h e co n trols, con necto r s and in d icators .
M ore information is given u nder Detaile d O p erating
Information .
DIS PL AY
P
ush B utton-Applies and
removes
logic
levels to t he oscilloscope system to enable or d isa b le
p lug-in operation . Switc h is functional on ly w hen
p l u g-in is op erate d in one of t he vertical d eflectio n
p l
u g-in
compartments .
Ο 2

P
OS Co
n
trols-
P ositions d is p lay vertically .
ι
BW L I M IT Pu s h B uttons-Allows re du ction of t he
upper b andwi d t h limit to increase t h e signal-to-noise
ratio for low-frequency applications . Selects upp er
ban dwi d t h limit
at
eit h er 1
mega
h ertz ( bu tton o u t) or
10 k ilo h ertz
(
bu tton in) .
O
PER ATI N G I N ST RU CTIO
N S
Section
1-5 Α
26
ST
EP ΑΤΤΕΝ B A L Ad j ustments- B ala n ces t h e in p ut
am p lifier for
minimum trace s h ift t hrou g h o u t t h e
d
eflection
factor
gain-switc h ing ra n ge .
Input Coup li n g P ush B uttons
AC-O U T:DC . B utton pus h e d in selects cap acitive
coupling of
signal app lie d to associate d+ or -
inp
ut
connecto
r ; button out selects d irect couplin g of inpu t
sig n al .
GND . Grou n d s t he preamplifier
in put
an
d connects
input signal to groun d t hroughα
1 mego h m resistor .
PRE CH G . B ot h AC and GN D
buttons pus hed in
p ermits p rec h arging of t
h e cou p ling cap acitor to t h e
input sig n al d o level . R
elease GN D button fo r
measurement .
M OD EP ush B utton s-Select c h annel to b e d is played
an d illumi n ate t h e p ro p er d eflection factor
setting
(1
Χ
or 10 Χ ) on
t he VO L TS/DI V switc h k no bsk irt .
B oth buttons pus hed i n provides α du al-trace d isplay .

Operating
Instructions-5A26
r
ο
Fig
.
1-
2 .
Front-panel controls, connectors, and indicators
.

Operating Instructions-5A26
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AC

O UT : DC
(b
utton out)
+ an d - In p
u t Connectors- BN C connectors for app li-
cation of external voltage signals
. Connector labele d

GND

GND ( bu tton in)
+ indicates t h at α p ositive-going signal will
cause
upwar d d eflectio n ; connector la b ele d - indicates
t
h
at

M OD E

CH
1 an d CH
2
α positive-going
sig n al will cause downwar d d eflectio n .

( b uttons in)
Con nectors
inclu de co d e d -
prob e
input rings for
activating t h e rea dou
t w hen using readout-co d e d
p robes .

d . A d j ust
intensity
control for normal viewing . Traces
sh oul d a pp ear
near gratic u le center .
B ASIC O PER ATIO N
e . Set t he VO L TS/D Ι V switc h es
to .1
. If
traces s h ift,
Preparation

a d ju st t he ST EP ΑΤΤΕΝ B A L control
as d
escri
bed in
'

T he following
procedures are i n te nded to h el p p lace t h e
trace
on t hesc r ee n q uic kly and prepare t he instrument for
immediate use :
'

α .
I n
sert 5 Α 26 all t he way into oscillosco p e plug-in
com p artment
.
ι
T R IGG ER Push Bu tton-Selects
time base triggeri n g
signal from eit h er channel .
b . Turn oscilloscope Intensity control to mi d ra n ge and
t u rn
oscilloscope syste m p ower on . P reset time-b ase
an
d
triggering
controls for 2 millisecon d / d ivision sweep rate
10

and a u tomatic triggeri
ng .
c . Set 5 Α 26 front- pan el controls as follows
:
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DIS
PL AY

ON (butto n in)
T RIGG ER

OU T : CH 1 (b u tto n
out)
P
OS

M i d ra nge
BW L I M IT

OU T : 1 MHz
(b utton o u t)
V O L TS/D 1 V

5
ST EP ΑΤΤΕΝ B A L

M
i d ra nge
C H 1 an d CH2
+Input
Cou p li n g
CH 1
and C
H 2 -
In
p
ut
Coupling
Step Attenuator B alance A dju stment proce
dure .
f .
M ove CH 1 trace 2 d ivisions b elow graticule h orizontal
centerline, and C H 2 trace to b ottom of graticule
with
P
OS controls .
g . Apply400 millivolt pea k
-to- p ea k signal fro m oscillo-
scope cali b rator loop wit hα test lea d or 1 Χ probeto
CH 1 + in p ut connector .
h .
R elease CH 1 + GND b utton . Disp lay will be α s qu ar e
wave 4 d
ivisions in amplitude with bottom of d is p lay at
refere n ce esta b lis hed in step (f) .
i . P osition b ottom of s q uare wave to graticule h
orizontal
centerline .
j . Pu s h in
C
H
1
+
AC button an d note that display s h ifts
d ownwar d 2 divisio n s .
k .
Disconnect test lead from CH 1 + in put an d connect
to CH
2 +
in pu t .
Ι. P ush in T RIGG
ER butto n for CH 2 triggering an d
repeat ste p s (f) t h
ro
ug h (j)
for CH2 operation .
AC

OU
T :
DC (button

Ste p
Attenuator B alance A d j ustment
Out)

Wh en t h e ST EP ΑΤΤΕΝ
B A L control is not properly a dj ust-
ed , t h e d is
p
lay
will s h ift vertically ( d ue to α do imbala nce i n
GND

G ND ( button in)

t he am p lifier)
as t h e VO L TS/DI V switc h is rotate d t h ro ugh -
out its range . T he
s h ift is more noticeable on t he most
sensitive positio n s .

Op
erating Instructions-5A26
α . Set VO L TS/DI V switch to 5 . Ground both
+ an d -

b . Wait about 1 second for coupling ca p acitor to ch
arge .
inputs (G N D bu ttons pu s h e d in) and p osition trace to
graticule h orizontal centerline .
c . R elease GND bu tton a n d ac com p
onent can b e meas u re d
in usual manner .
b . A dj ust ST EP
ΑΤΤΕΝ B A L control for minim u m
trace s h ift as VOL TS/DI V
switch is rotate d t h rou g ho u t
its range .

Signal In p ut Connectors
Wh en
connecting signals to t h e
+
an d - in p ut connectors
on
t he 5 Α 26,
consi d er t h e met h od of co up ling that will be

,
Gain C heck

u se d . Sometimes un s h iel d e d test leads can b e u se d to
Wh en t h e 5 Α 26 is first inserte d into α p lug-in com
p artment,

connect t h e 5 Α 26 to α signal sou rce, p artic
u larly w h e n α
t h e amplifier gain may be c heck e d an d ad
j usted if necessary .

h ig h level, low-frequency signal is
monitore d at α
low
i m -
See A d ju stment Proce d ure in Section 4 of t
h
is
manual for

p ed ance p oint . H
owever, w h en any of t h ese factors are
com p lete i n structions .

missing, it
becomes
i
n creasingly important to use s h iel d ed
signal
cab
les .
In
all cases, t he signal-trans p orting lea d s
s h ou l d be k e p t as s hort as practical .
D E TAI LE DO
PER ATING I NFO RM ATIO N
Applying Signals

Wh en ma k ing si n
gle-e nded
i
nput measurements (conve n tio n al
amplifier operation), b e sure to establis
h α common groun d
con nection between th e
d evice un d er test an d t he 5 Α 26 .
T h e s h iel dofα coaxial
cable is normally u se d for t h is pur pose .
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ι
If t h e maxim u m input voltage rating at t he gates
of t h e input FE T's is exceeded, t he gates a r e

In some cases, d
ifferential meas u rements re q uire no common
clampe d at about + or - 10 volts . If t h e signal

ground connection, a
nd
t
h erefore are less s u sce p tible to
sou r ce
can supply
m ore t ha n 1/16 ampere, t he

interference by ground-loop
currents . Some pro b lems wit h
input protective fuse(s) will o p e n .

stray magnetic co
u pling into t h e signal transporting leads
can also
be minimize d by u sing α d ifferential rat h er t
h
an α
single-en d e d measurement . T h ese consi d eratio n s are d is
Wh en meas u ring unk now n voltages, use t he h ig h
est deflection

cu sse d later in this sectio n under Differential O p eration .
factor first . If t he deflection is too small to ma
ke
t
he
meas u rement, switch to α lower deflectio n factor .
It is always im portant to consi der t h e signal so urce loa
d ing
(an d res u lting ch ange in t he source operating
c h aracteristics)

'
P re-C h arging

d u e to t he signal-trans p orting lea d s an d t he inpu t
circ u it of
Wh
en only t he ac com p onent of α signal having bot
hac and

t h e 5
Α 26
.
T h e circuit at t he in pu t connectors can normally
d o components is to b e measured, t
he
p re-c
h arge circ u it

b e re p rese n te d by α 1 mego h m resistance to ground p
arallel-
permits ch
arging
t
he
co
u p ling ca p acitor to t h e inpu t signal

ed by about 47 p icofarads . Α few
feet
of
s h iel ded ca b le

,
d
o
level .

(20 to 40 p icofara d s p er foot) may
increase t h e p arallel
capacitance to 100
picofarads or more . I n ma ny cases, t he
effects of th
ese resistive and cap acitive loa d s may be too
great and it may be desira b le to minimize t h em t
h
roug
h t h e

,
CAUTION

use of an attenuator pro be .
If t h e 5 Α 26 input is connected to α large d o
voltage sour ce (10 volts pea k or mo r e), use
t he p rech arge provision . Damage to t h e signal

Attenuator probes not only decrease t he resistive-ca p acitive
so u rce could
r esult since t he pea k current

loa d ing of α signal source, but also exten d t he measureme
n t
t hro u gh t h e ac coupling capacitor and t he

range of t h e 5 Α 26 to inclu d e substantially h
ig
h
er voltages .
input
protection
circuitry is limited only by

Passive atten u ator p rob es h avi n g attenuation
factors of 10 Χ ,

,
t
he
signal
source internal resistance .

100 Χ , and 1000Χ , as well as oth er s p ecial- pu r pose types,
are available t h roug h your Te ktronix F ield E ngineer or
F iel d Office .
α . B efore co n necting 5
Α
26
to α signal contai n ing α d o
com p one
n
t, p us
h
in
AC and G N D b uttons . T h en connect

Some measureme n t situations
re q uire an extremely h ig h
inpu t to
circ
u
it u nd er test .

resistance in pu t to t he 5 Α 26 with very
little sou rce loadi n g
ι
ι
1
1

ι
or signal attenuation . In s uc h situatio
n
s, α
passive attenuator

Deflection F actor
p robe cannot b e used . H
owever, t h is proble m may be solved

The amount of trace d eflection
produced by α signal is
'

by using α FE T Pr obe or t
heh ig h-imp e d ance i np ut p rovision

determi n e d by the signal am p litu d
e, t h e
atten
uation (if any)
of t h e 5 Α 26 as described un
d er H ig h -Impe d ance In pu t .

of t h e pro b e, th e setting of t h e
V
O
L TS/DI V switch , an d
t he setting of t h e
V
aria
b le control . T h e d eflection factor
settings
are calibrate d only w h en t he V ariable control is
H ig h-Im p edance In put

rotate d f u lly clockwise i n to t he deten t p osition .
In t h e 50 m t hro u gh 50 μ p
ositions of t he V O L TS/DI V
switch , w here thein
p ut attenuator is not used, t he internal
gate return resistors alone esta
b lis h t he 1 mego h m input

T he range of t he V aria b le control
is at least 2 .5 :1 . It provides
resistance . T he removal of t
he strap from t he P ream p lifier

uncalibrated d eflection factors
covering t h e full ra nge
circuit board (see
F ig . 4-4, C hannel 1 and 2 P reamplifier

between t
he
calibrate d
settings of t h e VO L TS/DI V switch .
circuit board com p onent an d test point
locations in t he

T he V ariable control can be set to exten d t he d eflection
Diagramsan d P arts L ists sectio n ) d isconnects t
hese resis-

factor to at least 12 .5 volts/ d ivision .
tors fro m groun d an d permits t he in pu t FE T
gates
to float,
p rovi d i n gαvery h ig hinput impe d ance
.
To re d uce
noise
and
obtain α more u sa b le d is p lay w he n t
he
V O L TS/DI V switc h is set to t h e more se n sitive p ositions,
T h e in pu t signal m u st be k ept to r elatively low amplit
u des,

p
u s h
in
t he BW L I M IT button to re d uce t h e b a n d wid t
hto
since t h e d eflection factor is restricte d to 50 millivolts/

10 kH z if t h is limit does not a ppreciably d istort t
hed esire d
d ivision t hr oug h 50 microvolts/ d ivision, an d d o cou p li n g

features of t h e signal u nde r ob servation .
must b e u se dto p rovi d eα d o p at h for t he
FE T
gate cu
rre n t .
V oltage Com p arison M easurements
O p
erating Instructions-5A26
NOTE

Some
a pp lications re q uire d eflection factors oth
er t han the
In t h e 0 .1 volt to 5 volt r ange of t he V O L TS/

fixe d values provided by t he V O L TS/DI V switch . One
suc h
DIV switc h , t he input impedance is pa
r alleled

app lication is comparison of signal am p litu d es by ratio
by t he resistors in t he attenuato r . W
h
en
t h e

rat h er th a n by absolute voltage . To accom p lis h t h is,
a
pp
ly
"

strap is removed, t he atten u ation ratio is

αreference
signal to eit h er
+or
- inputs of the 5A26, and
affected, causing t he deflectio nfacto r s in t h is

set the VO L TS/DI V switchand V aria b le con trol so
t h at
range to be incorrect .

To determine t
h e d e-

t he r eference dis p lay covers t h e d esire d
number of graticule
flect ί on factor, c h ec k t h e deflection with
an

d ivisio n s . Do not ch ange t
he V ariable con trol settings
input signal of k nown amplit
u de .

t h roug h out t he subse q uent
comparisons . H owever, th e
settings of t h e VO L TS/DI V switchcan be ch
ange dto
accommodate large ratios . In d
oing
so,
regard t h e nu m b ers
T h e signal source impedance is an
important factor, since

w h ic hdesignate t
h
e switc
h p ositions as r atio factors rat h er
gate cu rrent will p ro d uce an
offset . F or example, α 100

t h an voltages .
p icoampere gate cu
rrent
t
hrou g h 10 mego h ms produces α
1 millivolt
offset, w h ic h may result i n sig n ificant error
w h ere small voltages are of concern .

Differential O p eration
Single-en ded meas u rements
often yield unsatisfactory res u lts
beca
u se
of
interfe r ence resulting from ground-loop currents
T he h ig h -fre q uency res p onse will also d epen d upon t h e

b etween the 5 Α 26 and t he device un d er test . In oth er
signal sou rce im p eda n ce, si nce various s hu nt ca pacitances

cases, it may be d esirable to elimi n ate α do voltage
by means
b etween t h e source and t he input gate
m u
st
c harge an d
ot h er t han t he u se of α do block ing capacitor,
w h ic h co u l d
d isc h arge th roug h t h at i mp ed ance .

limit t he low-frequency res p onse
.
'

Dis p lay
P
olarity
T h ese limitations of
single-en de d measurements are effectively
Single-ended
signals
a pp
lie d to t he + in put connector pro-

eliminated by
connecting t h e
+
inp ut and - in p u t to
'

d uce α d is p lay in phase with
t he in p ut signal . Signals a pp lie d selecte dp oints
in t h e test circuit . Since t h e c h assis of t h e
to t he - i npu t connector
will be inverte d .

5 Α 26
nee d not be connecte d in any way to t he test circ u it,
t h ere are
few limitations to t h e selection of t h ese test points .
In any case, d
o
not
excee d t he maxim u m safe in pu t voltages .
Α similar
polarity relations h ip exists for d ifferentially a pp lie d
.

s ί gnals, but p
ertai ns
to
t h e direction of voltage c h ange at
one in put with res p ect to th e ot h e r , rat h er t han with res p ect

T h e + an d -AC bu ttons sh ou l d bothbe set to t
he
same
to c
h assis potential .

p
ositions, d epending on t he met hod of
signal coupling requ ire d .