Peak Atlas DCA55 User manual

Peak Atlas DCA
Semiconductor Component Analyser
Model DCA55
Designed and manufactured with pride in the UK
User Guide
© Peak Electronic Design Limited 2000/201
In the interests of development, information in this guide is subject to change without notice - E&OE
GB55-11

Atlas DCA User Guide September 201 – Rev 11
Page 2
Want to use it now?
We understand that you want to use your Atlas DCA right now. The
unit is ready to go and you should have little need to refer to this user
guide, but please make sure that you do at least take a look at the
notices on page !
Contents Page
Introduction....................................................................................3
Important Considerations...............................................................
Analysing semiconductors .............................................................5
Diodes......................................................................................7
Diode Networks.......................................................................8
LEDs........................................................................................9
Bicolour LEDs.......................................................................10
Bipolar Junction Transistors (BJTs).......................................11
Digital Transistors..................................................................18
Enhancement Mode MOSFETs .............................................19
Depletion Mode MOSFETs ...................................................20
Junction FETs (JFETs) ..........................................................21
Thyristors (SCRs) and Triacs.................................................22
Taking care of your Atlas DCA....................................................23
Battery replacement ...............................................................23
Self Tests ...............................................................................2
Appendix A - Technical Specifications........................................25
Appendix B - Warranty Information............................................26
Appendix C - Disposal information .............................................27

Atlas DCA User Guide September 201 – Rev 11
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Introduction
The Peak Atlas DCA is an intelligent semiconductor analyser that offers great
features together with refreshing simplicity. The Atlas DCA brings a world of
component data to your fingertips.
Summary Features:
• Automatic component type identification
 Bipolar transistors
 Darlington transistors
 Enhancement Mode MOSFETs
 Depletion Mode MOSFETs
 Junction FETs
 Low power sensitive Triacs
 Low power sensitive Thyristors
 Light Emitting Diodes
 Bicolour LEDs
 Diodes
 Diode networks
• Automatic pinout identification, just connect any way round.
• Special feature identification such as diode protection and resistor
shunts.
• Gain measurement for bipolar transistors.
• Leakage current measurement for bipolar transistors.
• Silicon and Germanium detection for bipolar transistors.
• Gate threshold measurement for Enhancement Mode MOSFETs.
• Semiconductor forward voltage measurement for diodes, LEDs and
transistor Base-Emitter junctions.
• Automatic and manual power-off.

Atlas DCA User Guide September 201 – Rev 11
Page
Important Considerations
Please observe the following guidelines:
• This instrument must NEVER be connected to powered
equipment/components or equipment/components with any
stored energy (e.g. charged capacitors). Failure to comply
with this warning may result in personal injury, damage to
the equipment under test, damage to the Atlas DCA and
invalidation of the manufacturer’s warranty.
• The Atlas DCA is designed to analyse semiconductors that
are not in-circuit, otherwise complex circuit effects will
result in erroneous measurements.
• Avoid rough treatment or hard knocks.
• This unit is not waterproof.
• Only use a good quality Alkaline battery.

Atlas DCA User Guide September 201 – Rev 11
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Analysing Components
The Atlas DCA is designed to analyse discrete,
unconnected, unpowered components. This
ensures that external connections don’t influence
the measured parameters. The three test probes can be
connected to the component any way round. If the component has
only two terminals, then any pair of the three test probes can be used.
The Atlas DCA will start component
analysis when the on-test button is
pressed.
Depending on the component type, analysis may take a few seconds to
complete, after which, the results of the analysis are displayed. Information is
displayed a “page” at a time, each page can be displayed by briefly pressing the
scroll-off button.
The arrow symbol on the display indicates that more pages are available
to be viewed.
Although the Atlas DCA will switch itself off if left unattended, you
can manually switch the unit off by holding down the scroll-off
button for a couple of seconds.
Atlas DCA55 Rx.x
is analysing....

Atlas DCA User Guide September 201 – Rev 11
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If the Atlas DCA cannot detect any
component between any of the test
probes, the following message will be
displayed:
If the component is not a supported
component type, a faulty component or
a component that is being tested in-
circuit, the analysis may result in the
following message being displayed:
Some components may be faulty due to
a shorted junction between a pair of the
probes. If this is the case, the following
message (or similar) will be displayed:
If all three probes are shorted (or very
low resistance) then the following
message will be displayed:
It is possible that the Atlas DCA may detect one or more diode
junctions or other component type within an unknown or faulty part.
This is because many semiconductors comprise of PN (diode)
junctions. Please refer to the section on diodes and diode networks for
more information.
No component
detected
Unknown/Faulty
component
Sho t ci cuit on
G een Blue
Sho t ci cuit on
Red G een Blue

Atlas DCA User Guide September 201 – Rev 11
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Diodes
The Atlas DCA will analyse almost any type of
diode. Any pair of the three test clips can be
connected to the diode, any way round. If the
unit detects a single diode, the following
message will be displayed:
Pressing the scroll-off
button will then display the pinout for
the diode. In this example, the Anode of
the diode is connected to the Red test
clip and the Cathode is connected to the
Green test clip, additionally, the Blue
test clip is unconnected. The forward
voltage drop is then displayed, this gives
an indication of the diode technology. In
this example, it is likely that the diode is
a silicon diode. A germanium or
Schottky diode may yield a forward
voltage of about 0.25V. The current at
which the diode was tested is also
displayed.
Note that the Atlas DCA will detect only one diode even if two diodes
are connected in series when the third test clip is not connected to the
junction between the diodes. The forward voltage drop displayed
however will be the voltage across the whole series combination.
The Atlas DCA will determine that the diode(s) under test is an LED
if the measured forward voltage drop exceeds 1.50V. Please refer to
the section on LED analysis for more information.
Diode o diode
junction(s)
RED GREEN BLUE
Anod Cath
Fo wa d voltage
Vf=0.67V
Test cu ent
If=4.62mA

Atlas DCA User Guide September 201 – Rev 11
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Diode Networks
The Atlas DCA will intelligently identify popular types of
three terminal diode networks. For three terminal devices
such as SOT-23 diode networks, the three test clips must all
be connected, any way round. The instrument will identify the type of diode
network and then display information regarding each detected diode in
sequence. The following types of diode networks are automatically recognised
by the Atlas DCA:
Both cathodes connected
together, such as the BAV70
device.
Anodes of each diode are
connected together, the
BAW56W is an example.
Here, each diode is connected
in series. An example is the
BAV99.
Following the component identification,
the details of each diode in the network
will be displayed.
Firstly, the pinout for the diode is
displayed, followed by the electrical
information, forward voltage drop and
the current at which the diode was
tested. The value of the test current
depends on the measured forward
voltage drop of the diode.
Following the display of all the details for the first diode, the details of the
second diode will then be displayed.
Common cathode
diode netwo k
Common anode
diode netwo k
Se ies
diode netwo k
Pinout fo D1...
RED GREEN BLUE
Cath Anod
Fo wa d voltage
D1 Vf=0.64V

Atlas DCA User Guide September 201 – Rev 11
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LEDs
An LED is really just another type of diode, however, the
Atlas DCA will determine that an LED or LED network has
been detected if the measured forward voltage drop is larger
than 1.5V. This also enables the Atlas DCA to intelligently
identify bicolour LEDs, both two-terminal and three-terminal varieties.
Like the diode analysis, the pinout, the
forward voltage drop and the associated
test current is displayed.
Here, the Cathode (-ve) LED terminal is
connected to the Green test clip and the
Anode (+ve) LED terminal is connected
to the Blue test clip.
In this example, a simple green LED
yields a forward voltage drop of 1.92V.
The test current is dependant on the
forward voltage drop of the LED, here
the test current is measured as 3.28mA.
Some blue LEDs (and their cousins, white LEDs) require high
forward voltages and may not be detected by the Atlas DCA.
LED o diode
junction(s)
RED GREEN BLUE
Cath Anod
Fo wa d voltage
Vf=1.92V
Test cu ent
If=3.28mA

Atlas DCA User Guide September 201 – Rev 11
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Bicolour LEDs
Bicolour LEDs are automatically identified. If your LED has 3
leads then ensure they are all connected, in any order.
A two terminal bicolour LED consists of two LED chips which
are connected in inverse parallel within the LED body. Three terminal bicolour
LEDs are made with either common anodes or common cathodes.
Here a two terminal LED
has been detected.
This message will be
displayed if the unit has
detected a three terminal
LED.
The details of each LED in the package
will then be displayed in a similar way
to the diode networks detailed earlier.
The pinout for the 1
st
LED is displayed.
Remember that this is the pinout for just
one of the two LEDs in the package.
Interestingly, the voltage drops for each
LED relate to the different colours
within the bicolour LED. It may
therefore be possible to determine which
lead is connected to each colour LED
within the device. Red LEDs often have
the lowest forward voltage drop,
followed by yellow LEDs, green LEDs
and finally, blue LEDs.
Two te minal
bicolou LED
Th ee te minal
bicolou LED
Pinout fo D1...
RED GREEN BLUE
Anod Cath
Fo wa d voltage
D1 Vf=1.98V
Test cu ent
D1 If=3.22mA

Atlas DCA User Guide September 201 – Rev 11
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Bipolar Junction ransistors (BJ s)
Bipolar Junction Transistors are simply “conventional”
transistors, although variants of these do exist such as
Darlingtons, diode protected (free-wheeling diode), resistor
shunted types and combinations of these types. All of these
variations are automatically identified by the Atlas DCA.
Bipolar Junction Transistors are
available in two main types, NPN and
PNP. In this example, the unit has
detected a Silicon PNP transistor.
The unit will determine that the
transistor is Germanium only if the base-
emitter voltage drop is less than 0.55V.
If the device is a Darlington transistor (two BJTs connected
together), the unit will
display a similar
message to this:
Note that the Atlas DCA will determine that the transistor under test is
a Darlington type if the base-emitter voltage drop is greater than
1.00V for devices with a base-emitter shunt resistance of greater than
60kΩ or if the base-emitter voltage drop is greater than 0.80V for
devices with a base-emitter shunt resistance of less than 60kΩ. The
measured base-emitter voltage drop is displayed as detailed later in
this section.
PNP Silicon
T ansisto
PNP Ge manium
T ansisto
NPN Da lington
T ansisto

Atlas DCA User Guide September 201 – Rev 11
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Pressing the scroll-off button will result in the transistor’s pinout being
displayed.
Here, the instrument has identified that
the Base is connected to the Red test
clip, the Collector is connected to the
Green test clip and the Emitter is
connected to the Blue test clip.
ransistor Special Features
Many modern transistors contain additional special features. If the Atlas DCA
has detected any special features, then the details of these features are
displayed next after pressing the scroll-off button. If there are no special
features detected then the next screen will be the transistor’s current gain.
Some transistors, particularly CRT
deflection transistors and many large
Darlingtons have a protection diode
inside their package connected between
the collector and emitter.
The Philips BU505DF is a typical example of a diode protected bipolar
transistor. Remember that protection diodes are always internally connected
between the collector and the emitter so that they are
normally reverse biased.
For NPN transistors, the anode of the diode is connected to
the emitter of the transistor. For PNP transistors, the anode
of the diode is connected to the collector of the transistor.
RED GREEN BLUE
Base Coll Emit
Diode p otection
between C-E

Atlas DCA User Guide September 201 – Rev 11
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Additionally, many Darlingtons and a few non-Darlington transistors also have
a resistor shunt network between the base and emitter of the device.
The Atlas DCA can detect the resistor shunt if it has a
resistance of typically less than 60kΩ.
The popular Motorola TIP110 NPN Darlington
transistor contains internal resistors between the base
and emitter.
When the unit detects the presence of a
resistive shunt between the base and
emitter, the display will show:
Additionally, the Atlas DCA will warn
you that the accuracy of gain
measurement (h
FE
) has been affected by
the shunt resistor.
It is important to note that if a transistor does contain a base-emitter
shunt resistor network, any measurements of current gain (h
FE
) will be
very low at the test currents used by the Atlas DCA. This is due to the
resistors providing an additional path for the base current. The
readings for gain however can still be used for comparing transistors
of a similar type for the purposes of matching or gain band selecting.
The Atlas DCA will warn you if such a condition arises as illustrated
above.
Resisto shunt
between B-E
h
FE
not accu ate
due to B-E es

Atlas DCA User Guide September 201 – Rev 11
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Faulty or Very Low Gain ransistors
Faulty transistors that exhibit very low gain
may cause the Atlas DCA to only identify one
or more diode junctions within the device. This
is because NPN transistors consist of a
structure of junctions that behave like a
common anode diode network. PNP transistors
can appear to be common cathode diode
networks. The common junction represents the base terminal. This is normal
for situations where the current gain is
so low that it is immeasurable at the test
currents used by the Atlas DCA.
Please note that the equivalent diode pattern may not be correctly
identified by the Atlas DCA if your transistor is a darlington type or
has additional diode(s) in its package (such as a collector-emitter
protection diode). This is due to multiple pn junctions that cannot be
uniquely analysed.
In some circumstances, the unit may not be able to deduce anything sensible
from the device at all, in which case you will see either of these messages:
B
C
E
Common anode
diode netwo k
Unknown/Faulty
component
No component
detected

Atlas DCA User Guide September 201 – Rev 11
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Current Gain (h
FE
)
The DC current gain (h
FE
) is displayed
after any special transistor features have
been displayed.
DC current gain is simply the ratio of the
collector current (less leakage) to the
base current for a particular operating
condition. The Atlas DCA measures h
FE
at a collector current of 2.50mA and a
collector-emitter voltage of between 2V
and 3V.
The gain of all transistors can vary
considerably with collector current,
collector voltage and also temperature.
The displayed value for gain therefore
may not represent the gain experienced
at other collector currents and voltages.
This is particularly true for large
devices.
Darlington transistors can have very high gain values and more variation of
gain will be evident as a result of this.
Additionally, it is quite normal for transistors of the same type to have a wide
range of gain values. For this reason, transistor circuits are often designed so
that their operation has little dependence on the absolute value of current gain.
The displayed value of gain is very useful however for comparing transistors of
a similar type for the purposes of gain matching or fault finding.
Cu ent gain
h
FE
=126
Test cu ent
Ic=2.50mA
I
C
=2.5mA
I
-I
(I = leakage
current)
C
Cleak
Cleak
h
F
=
I
B
I
B

Atlas DCA User Guide September 201 – Rev 11
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Base-Emitter Voltage Drop
The DC characteristics of the base-emitter
junction are displayed, both the base-emitter
forward voltage drop and the base current
used for the measurement.
The forward base-emitter voltage drop
can aid in the identification of silicon or
germanium devices. Germanium devices
can have base-emitter voltages as low as
0.2V, Silicon types exhibit readings of
about 0.7V and Darlington transistors
can exhibit readings of about 1.2V because of the multiple base-emitter
junctions being measured.
Note that the Atlas DCA does not perform the base-emitter tests at the
same base current as that used for the current gain measurement.
B-E Voltage
Vbe=0.77V
Test cu ent
Ib=4.52mA
IB
VB

Atlas DCA User Guide September 201 – Rev 11
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Collector Leakage Current
The collector current that takes place
when no base current is flowing is
referred to as Leakage Current.
Most modern transistor exhibit
extremely low values of leakage
current, often less than 1µA, even for
very high collector-emitter voltages.
Older Germanium types however can
suffer from significant collector leakage
current, particular at high temperatures
(leakage current can be very temperature
dependant).
If your transistor is a Silicon type, you should expect to see a leakage current of
close to 0.00mA unless the transistor is faulty.
I
C
Leakage
IB = 0
Leakage cu ent
Ic=0.17mA

Atlas DCA User Guide September 201 – Rev 11
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Digital ransistors
Digital transistors aren’t really digital, they can act in
both a linear or fully on/off mode. They’re called
“digital transistors” because they can be driven
directly to digital outputs without the need for current
limiting resistors.
These parts are most often found in surface mount packages but
are becoming more common, particularly in mass produced
electronic products.
The presence of the base resistor (and
the base-emitter shunt resistor) means
that it isn’t possible for the Atlas DCA
to measure the gain of the device, so
only the device polarity (NPN/PNP)
and pinout is shown.
B
C
E
NPN Digital
T ansisto
RED GREEN BLUE
Emit Base Coll

Atlas DCA User Guide September 201 – Rev 11
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Enhancement Mode MOSFE s
MOSFET stands for Metal Oxide Semiconductor Field Effect
Transistor. Like bipolar transistors, MOSFETs are available in
two main types, N-Channel and P-Channel. Most modern
MOSFETs are of the Enhancement Mode type, meaning that
the bias of the gate-source voltage is
always positive (For N-Channel types).
The other (rarer) type of MOSFET is the
Depletion Mode type which is described
in a later section.
MOSFETs of all types are sometimes known as IGFETs, meaning Insulated
Gate Field Effect Transistor. This term describes a key feature of these
devices, an insulated gate region that results in negligible gate current for both
positive and negative gate-source voltages (up to the maximum allowed values
of course, typically ±20V).
The first screen to be displayed gives information on the type of MOSFET
detected. Pressing scroll-off will then
result in the pinout of the MOSFET being
displayed. The gate, source and drain are
each identified.
An important feature of a MOSFET is the
gate-source threshold voltage, the gate-
source voltage at which conduction
between the source and drain starts. The
gate threshold is displayed following the
pinout information.
The Atlas DCA detects that drain-source conduction has started when it
reaches 2.50mA.
Enhancement mode
N-Ch MOSFET
RED GREEN BLUE
Gate D n S ce
Gate Th eshold
Vgs=3.47V
Test cu ent
Id=2.50mA

Atlas DCA User Guide September 201 – Rev 11
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Depletion Mode MOSFE s
The fairly rare Depletion Mode MOSFET is very similar to the
conventional Junction FET (JFET) except that the gate
terminal is insulated from the other two terminals. The input
resistance of these devices can typically be greater than
1000MΩ for negative and positive gate-source voltages.
Depletion Mode devices are
characterised by the gate-source voltage
required to control the drain-source
current.
Modern Depletion Mode devices are generally only available in N-Channel
varieties and will conduct current between its drain and source terminals even
with a zero voltage applied across the gate and the source. The device can only
be turned completely off by taking its gate significantly more negative than its
source terminal, say –10V. It is this characteristic that makes them so similar to
conventional JFETs.
Pressing scroll-off will cause the
pinout screen to be displayed.
Depletion mode
N-Ch MOSFET
RED GREEN BLUE
D n Gate S ce