Peak Atlas DCA55 User manual

Atlas DCA55
Semiconductor Component Analyser
Model DCA55 (Firmware: 4.1)
Designed and manu actured with pride in the UK
User Guide
© Peak Electronic Design Limited 2000/2021
In the interests o development, in ormation in this guide is subject to change without notice.
E&OE
EN55-14

DCA55 User Guide November 2021 – Rev 14
Page 2
Want to use it now?
We understand that you want to use your DCA55 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 4!
Contents Page
Introduction ................................................................................... 3
Important onsiderations .............................................................. 4
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 (S Rs) and Triacs ................................................ 22
Taking care of your D A55 ........................................................ 23
Battery replacement .............................................................. 23
Self Tests ............................................................................... 24
Appendix A - Technical Specifications ....................................... 25
Appendix B - Statutory Information ............................................ 28
This user guide has been written to accompany the DCA55 with revision 4.1
firmware. Other revisions of firmware may differ in operation, features and
specifications. The firmware version is displayed briefly upon power-up.

DCA55 User Guide November 2021 – Rev 14
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Introduction
The Peak Atlas DCA55 is an intelligent semiconductor analyser that offers
great features together with refreshing simplicity. The DCA55 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.
(only the gate is identified on JFETs)
 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.

DCA55 User Guide November 2021 – Rev 14
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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 DCA55 and
invalidation of the manufacturer’s warranty.
 The DCA55 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 battery (details on page 23).

DCA55 User Guide November 2021 – Rev 14
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Analysing Components
The DCA55 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 DCA55 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 DCA55 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.
Peak Atlas DCA
model DCA55 Rx.x

DCA55 User Guide November 2021 – Rev 14
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If the DCA55 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 DCA55 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
Short c rcu t on
Green Blue
Short c rcu t on
Red Green Blue

DCA55 User Guide November 2021 – Rev 14
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Diodes
The DCA55 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
athode 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 DCA55 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 DCA55 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.
D ode or d ode
junct on(s)
RED GREEN BLUE
Anod Cath
Forward voltage
Vf=0.677V
Test current
If=4.300mA

DCA55 User Guide November 2021 – Rev 14
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Diode Networks
The DCA55 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 DCA55:
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
d ode network
Common anode
d ode network
Ser es
d ode network
P nout for D1...
RED GREEN BLUE
Cath Anod
Forward voltage
D1 Vf=0.642V

DCA55 User Guide November 2021 – Rev 14
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LEDs
An LED is really just another type of diode, however, the
DCA55 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 DCA55 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 athode (-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
1.936V.
The test current is dependant on the
forward voltage drop of the LED, here
the test current is measured as
3.047mA.
 Some blue LEDs (and their cousins, white LEDs) require high
forward voltages and may not be detected by the DCA55.
LED or d ode
junct on(s)
RED GREEN BLUE
Cath Anod
Forward voltage
Vf=1.936V
Test current
If=3.047mA

DCA55 User Guide November 2021 – Rev 14
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icolour 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 drop for each
LED (loosely) relates 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 term nal
b colour LED
Three term nal
b colour LED
P nout for D1...
RED GREEN BLUE
Anod Cath
Forward voltage
D1 Vf=1.950V
Test current
D1 If=3.033mA

DCA55 User Guide November 2021 – Rev 14
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ipolar Junction Transistors ( JTs)
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 DCA55.
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 DCA55 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 60k
or if the base-emitter voltage drop is greater than 0.80V for devices
with a base-emitter shunt resistance of less than 60k. The measured
base-emitter voltage drop is displayed as detailed later in this section.
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 ollector is connected
to the Green test clip and the Emitter is
connected to the Blue test clip.
PNP S l con
Trans stor
PNP German um
Trans stor
NPN Darl ngton
Trans stor
RED GREEN BLUE
Base Coll Em t

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Transistor Special Features
Many modern transistors contain additional special features. If the DCA55 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 RT
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.
D ode protect on
between C-E

DCA55 User Guide November 2021 – Rev 14
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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 DCA55 can detect the resistor shunt if it has a
resistance of typically less than 60k.
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 DCA55 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 DCA55. 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 DCA55 will warn you if such a condition arises as illustrated
above.
Res stor shunt
between B-E
h FE not accurate
due to B-E res

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Faulty or Very Low Gain Transistors
Faulty transistors that exhibit very low gain
may cause the DCA55 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 DCA55.
Please note that the equivalent diode pattern may not be correctly
identified by the DCA55 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
d ode network
Unknown/Faulty
component
No component
detected

DCA55 User Guide November 2021 – Rev 14
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Current Gain (h
FE
)
The D current gain (h
FE
) is displayed
after any special transistor features have
been displayed.
D current gain is simply the ratio of the
collector current (less leakage) to the
base current for a particular operating
condition. The DCA55 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.
Current ga n
h FE =126
Test current
Ic=2.50mA
I
C
=2.5mA
I -
I
(I = leakage
current)
C
Cleak
Cle
ak
h
FE
=
I
B
I
B

DCA55 User Guide November 2021 – Rev 14
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ase-Emitter Voltage Drop
The D 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.
Base-Emitter voltage drop measurements can be useful when
matching transistors.
Note that the DCA55 does not perform the base-emitter tests at the
same base current as that used for the current gain measurement.
B-E Voltage
Vbe=0.664V
Test current
Ib=4.312mA
IB
VBE

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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 (I
EO
).
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 0.000mA unless the transistor is faulty.
The minimum leakage current that the DCA55 can measure is
typically 10μA (0.010mA). For leakage currents higher than 10μA,
the measurement resolution is typically 2μA (0.002mA). The
maximum allowed leakage current for the DCA55 is 0.2mA for
silicon devices and 1.75mA for germanium devices. If the leakage
current is more than that allowed value then the D A55 may not
detect your device correctly.
During the leakage current measurement, the base-emitter is automatically
shunted with a 910k resistor to reduce the influence of stray pick-up on an
otherwise floating base lead. Please note however that leakage current is
influenced by the base circuitry. For example, in the target application, the
collector-emitter leakage current can be reduced by having a lower value
resistance across the base-emitter.
The measured leakage current here however can be used to compare devices
of the same type.
I
C
Leakage
IB = 0
Leakage current
Ic=0.170mA

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Digital Transistors
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 by digital outputs without the need for base
current limiting resistors.
These parts are most often found in surface mount packages and
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 DCA55 to
measure the gain of the device, so only
the device polarity (NPN/PNP) and
pinout is shown.
B
C
E
NPN D g tal
Trans stor
RED GREEN BLUE
Em t Base Coll

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Enhancement Mode MOSFETs
MOSFET stands for Metal Oxide Semiconductor Field Effect
Transistor. Like bipolar transistors, MOSFETs are available
in two main types, N- hannel and P- hannel. Most modern
MOSFETs are of the Enhancement Mode type, meaning that
the bias of the gate-source voltage is always positive (For N- hannel 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 DCA55 detects that drain-source
conduction has started when it reaches
2.50mA.
Enhancement mode
N-Ch MOSFET
RED GREEN BLUE
Gate Drn Srce
Gate Threshold
Vgs=3.47V
Test current
Id=2.50mA

DCA55 User Guide November 2021 – Rev 14
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Depletion Mode MOSFETs
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
1000M 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- hannel
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.
Deplet on mode
N-Ch MOSFET
RED GREEN BLUE
Drn Gate Srce