1. Product profile
1.1 General description
NPN general-purpose transistors in small plastic packages.
[1] /DG: halogen-free
[2] Also available in SOT54A and SOT54 variant packages (see Section 2).
BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
Rev. 07 — 10 December 2008 Product data sheet
Table 1. Product overview
Type number[1] Package PNP complement
NXP JEITA JEDEC
BC847 SOT23 - TO-236AB BC857
BC847A BC857A
BC847B BC857B
BC847B/DG -
BC847C BC857C
BC847W SOT323 SC-70 - BC857W
BC847AW BC857AW
BC847BW BC857BW
BC847BW/DG -
BC847CW BC857CW
BC847T SOT416 SC-75 - BC857T
BC847AT BC857AT
BC847AT/DG -
BC847BT BC857BT
BC847CT BC857CT
BC847AM SOT883 SC-101 - BC857AM
BC847BM BC857BM
BC847CM BC857CM
BC547[2] SOT54 SC-43A TO-92 BC557[2]
BC547B[2] BC557B[2]
BC547C[2] BC557C[2]
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 2 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
1.2 Features
nLow current
nLow voltage
nThree different gain selections
1.3 Applications
nGeneral-purpose switching and amplification
1.4 Quick reference data
2. Pinning information
Table 2. Quick reference data
Symbol Parameter Conditions Min Typ Max Unit
VCEO collector-emitter voltage open base - - 45 V
ICcollector current - - 100 mA
hFE DC current gain VCE =5V; I
C= 2 mA 110 - 800
hFE group A 110 180 220
hFE group B 200 290 450
hFE group C 420 520 800
Table 3. Pinning
Pin Description Simplified outline Graphic symbol
SOT23, SOT323, SOT416
1 base
2 emitter
3 collector
SOT883
1 base
2 emitter
3 collector
006aaa144
12
3
sym021
3
2
1
3
1
2
Transparent
top view
sym021
3
2
1
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 3 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
3. Ordering information
SOT54
1 emitter
2 base
3 collector
SOT54A
1 emitter
2 base
3 collector
SOT54 variant
1 emitter
2 base
3 collector
Table 3. Pinning
…continued
Pin Description Simplified outline Graphic symbol
001aab347
1
2
3
sym026
3
1
2
001aab348
1
2
3
sym026
3
1
2
001aab447
1
2
3
sym026
3
1
2
Table 4. Ordering information
Type number[1] Package
Name Description Version
BC847 - plastic surface-mounted package; 3 leads SOT23
BC847A
BC847B
BC847B/DG
BC847C
BC847W SC-70 plastic surface-mounted package; 3 leads SOT323
BC847AW
BC847BW
BC847BW/DG
BC847CW
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 4 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
[1] /DG: halogen-free
[2] Also available in SOT54 and SOT54 variant packages (see Section 2 and Section 9).
4. Marking
[1] /DG: halogen-free
[2] * = -: made in Hong Kong
* = p: made in Hong Kong
* = t: made in Malaysia
* = W: made in China
BC847T SC-75 plastic surface-mounted package; 3 leads SOT416
BC847AT
BC847AT/DG
BC847BT
BC847CT
BC847AM SC-101 leadless ultra small plastic package; 3 solder lands;
body 1.0 ×0.6 ×0.5 mm SOT883
BC847BM
BC847CM
BC547[2] SC-43A plastic single-ended leaded (through hole) package;
3 leads SOT54
BC547B[2]
BC547C[2]
Table 4. Ordering information
…continued
Type number[1] Package
Name Description Version
Table 5. Marking codes
Type number[1] Marking code[2] Type number[1] Marking code[2]
BC847 1H* BC847AT 1E
BC847A 1E* BC847AT/DG B5
BC847B 1F* BC847BT 1F
BC847B/DG *BC BC847CT 1G
BC847C 1G* BC847AM D4
BC847W 1H* BC847BM D5
BC847AW 1E* BC847CM D6
BC847BW 1F* BC547 C547
BC847BW/DG G9* BC547B C547B
BC847CW 1G* BC547C C547C
BC847T 1N - -
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 5 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
5. Limiting values
[1] Device mounted on an FR4 Printed-Circuit Board (PCB), single-sided copper, tin-plated and standard
footprint.
[2] Reflow soldering is the only recommended soldering method.
[3] Device mounted on an FR4 PCB with 60 µm copper strip line, standard footprint.
6. Thermal characteristics
[1] Device mounted on an FR4 PCB, single-sided copper, tin-plated and standard footprint.
[2] Reflow soldering is the only recommended soldering method.
[3] Device mounted on an FR4 PCB with 60 µm copper strip line, standard footprint.
Table 6. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol Parameter Conditions Min Max Unit
VCBO collector-base voltage open emitter - 50 V
VCEO collector-emitter voltage open base - 45 V
VEBO emitter-base voltage open collector - 6 V
ICcollector current - 100 mA
ICM peak collector current single pulse;
tp≤1ms - 200 mA
IBM peak base current single pulse;
tp≤1ms - 100 mA
Ptot total power dissipation Tamb ≤25 °C
SOT23 [1] - 250 mW
SOT323 [1] - 200 mW
SOT416 [1] - 150 mW
SOT883 [2][3] - 250 mW
SOT54 [1] - 500 mW
Tjjunction temperature - 150 °C
Tamb ambient temperature −65 +150 °C
Tstg storage temperature −65 +150 °C
Table 7. Thermal characteristics
Symbol Parameter Conditions Min Typ Max Unit
Rth(j-a) thermal resistance from
junction to ambient in free air
SOT23 [1] - - 500 K/W
SOT323 [1] - - 625 K/W
SOT416 [1] - - 833 K/W
SOT883 [2][3] - - 500 K/W
SOT54 [1] - - 250 K/W
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 6 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
7. Characteristics
[1] Pulse test: tp≤300 µs; δ≤0.02.
[2] VBE decreases by approximately 2 mV/K with increasing temperature.
Table 8. Characteristics
T
amb
= 25
°
C unless otherwise specified.
Symbol Parameter Conditions Min Typ Max Unit
ICBO collector-basecut-off
current VCB =30V; I
E=0A --15nA
VCB =30V; I
E=0A;
Tj= 150 °C--5µA
IEBO emitter-base cut-off
current VEB =5V; I
C= 0 A - - 100 nA
hFE DC current gain
hFE group A VCE =5V; I
C=10µA - 90 -
hFE group B VCE =5V; I
C=10µA - 150 -
hFE group C VCE =5V; I
C=10µA - 270 -
DC current gain VCE =5V; I
C= 2 mA 110 - 800
hFE group A VCE =5V; I
C= 2 mA 110 180 220
hFE group B VCE =5V; I
C= 2 mA 200 290 450
hFE group C VCE =5V; I
C= 2 mA 420 520 800
VCEsat collector-emitter
saturation voltage IC= 10 mA; IB= 0.5 mA - 90 200 mV
IC= 100 mA; IB=5mA [1] - 200 400 mV
VBEsat base-emitter
saturation voltage IC= 10 mA; IB= 0.5 mA [2] - 700 - mV
IC= 100 mA; IB=5mA [2] - 900 - mV
VBE base-emitter voltage IC= 2 mA; VCE =5V [2] 580 660 700 mV
IC= 10 mA; VCE = 5 V - - 770 mV
Cccollector capacitance IE=i
e= 0 A; VCB =10V;
f=1MHz - - 1.5 pF
Ceemitter capacitance IC=i
c= 0 A; VEB = 0.5 V;
f=1MHz -11-pF
fTtransition frequency IC= 10 mA; VCE =5V;
f = 100 MHz 100 - - MHz
NF noise figure IC= 200 µA; VCE =5V;
RS=2kΩ; f = 1 kHz;
B = 200 Hz
- 2 10 dB
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 7 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
VCE =5V
(1) Tamb = 150 °C
(2) Tamb =25°C
(3) Tamb =−55 °C
VCE =5V
(1) Tamb =−55 °C
(2) Tamb =25°C
(3) Tamb = 150 °C
Fig 1. Selection A: DC current gain as a function of
collector current; typical values Fig 2. Selection A: Base-emitter voltage as a
function of collector current; typical values
IC/IB=20
(1) Tamb = 150 °C
(2) Tamb =25°C
(3) Tamb =−55 °C
IC/IB=10
(1) Tamb =−55 °C
(2) Tamb =25°C
(3) Tamb = 150 °C
Fig 3. Selection A: Collector-emitter saturation
voltage as a function of collector current;
typical values
Fig 4. Selection A: Base-emitter saturation voltage
as a function of collector current; typical
values
mgt723
10−111010
2103
IC (mA)
0
400
300
200
100
hFE
(1)
(2)
(3)
mgt724
10−111010
2103
IC (mA)
0
1200
1000
800
600
400
200
VBE
(mV)
(1)
(2)
(3)
103
102
10
mgt725
10−111010
2103
IC (mA)
VCEsat
(mV)
(1)
(2)
(3)
mgt726
10−111010
2103
IC (mA)
0
1200
1000
800
600
400
200
VBEsat
(mV)
(1)
(2)
(3)
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 8 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
VCE =5V
(1) Tamb = 150 °C
(2) Tamb =25°C
(3) Tamb =−55 °C
VCE =5V
(1) Tamb =−55 °C
(2) Tamb =25°C
(3) Tamb = 150 °C
Fig 5. Selection B: DC current gain as a function of
collector current; typical values Fig 6. Selection B: Base-emitter voltage as a
function of collector current; typical values
IC/IB=20
(1) Tamb = 150 °C
(2) Tamb =25°C
(3) Tamb =−55 °C
IC/IB=10
(1) Tamb =−55 °C
(2) Tamb =25°C
(3) Tamb = 150 °C
Fig 7. Selection B: Collector-emitter saturation
voltage as a function of collector current;
typical values
Fig 8. Selection B: Base-emitter saturation voltage
as a function of collector current; typical
values
mgt727
10−111010
2103
IC (mA)
0
600
500
400
300
200
100
hFE
(1)
(2)
(3)
0
1200
1000
800
600
400
200
mgt728
10−210−111010
2103
IC (mA)
VBE
(mV)
(1)
(2)
(3)
104
103
102
10
mgt729
10−111010
2103
IC (mA)
VCEsat
(mV)
(1)
(2)
(3)
mgt730
10−111010
2103
IC (mA)
0
1200
1000
800
600
400
200
VBEsat
(mV)
(1)
(2)
(3)
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 9 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
VCE =5V
(1) Tamb = 150 °C
(2) Tamb =25°C
(3) Tamb =−55 °C
VCE =5V
(1) Tamb =−55 °C
(2) Tamb =25°C
(3) Tamb = 150 °C
Fig 9. Selection C: DC current gain as a function of
collector current; typical values Fig 10. Selection C: Base-emitter voltage as a
function of collector current; typical values
IC/IB=20
(1) Tamb = 150 °C
(2) Tamb =25°C
(3) Tamb =−55 °C
IC/IB=10
(1) Tamb =−55 °C
(2) Tamb =25°C
(3) Tamb = 150 °C
Fig 11. Selection C: Collector-emitter saturation
voltage as a function of collector current;
typical values
Fig 12. Selection C: Base-emitter saturation voltage
as a function of collector current; typical
values
mgt731
10−111010
2103
IC (mA)
0
1200
1000
800
600
400
200
hFE
(1)
(2)
(3)
0
1200
1000
800
600
400
200
mgt732
10−210−111010
2103
IC (mA)
VBE
(mV)
(1)
(2)
(3)
104
103
102
10
mgt733
10−111010
2103
IC (mA)
VCEsat
(mV)
(1)
(2)(3)
mgt734
10−111010
2103
IC (mA)
0
1200
1000
800
600
400
200
VBEsat
(mV)
(1)
(2)
(3)
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 10 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
8. Package outline
Fig 13. Package outline SOT23 (TO-236AB) Fig 14. Package outline SOT323 (SC-70)
Fig 15. Package outline SOT416 (SC-75) Fig 16. Package outline SOT883 (SC-101)
Fig 17. Package outline SOT54 (SC-43A/TO-92) Fig 18. Package outline SOT54A
04-11-04Dimensions in mm
0.45
0.15
1.9
1.1
0.9
3.0
2.8
2.5
2.1 1.4
1.2
0.48
0.38 0.15
0.09
12
3
04-11-04Dimensions in mm
0.45
0.15
1.1
0.8
2.2
1.8
2.2
2.0 1.35
1.15
1.3
0.4
0.3 0.25
0.10
12
3
04-11-04Dimensions in mm
0.95
0.60
1.8
1.4
1.75
1.45 0.9
0.7
0.25
0.10
1
0.30
0.15
12
30.45
0.15
03-04-03Dimensions in mm
0.62
0.55
0.55
0.47 0.50
0.46
0.65
0.20
0.12
3
21
0.30
0.22
0.30
0.22
1.02
0.95
0.35
04-11-16Dimensions in mm
5.2
5.0 14.5
12.7
4.8
4.4
4.2
3.6 0.45
0.38
0.48
0.40
1.27 2.54
3
2
1
04-06-28Dimensions in mm
5.2
5.0 14.5
12.7
4.8
4.4
4.2
3.6 0.45
0.38
0.48
0.40
2.54
5.08
3 max
3
2
1
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 11 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
9. Packing information
Fig 19. Package outline SOT54 variant
05-01-10Dimensions in mm
5.2
5.0 14.5
12.7
4.8
4.4
4.2
3.6
0.45
0.38
0.48
0.40
1.27
1.27
2.54
2.5
max
3
2
1
Table 9. Packing methods
The indicated -xxx are the last three digits of the 12NC ordering code.
[1]
Type number[2] Package Description Packing quantity
3000 5000 10000
BC847 SOT23 4 mm pitch, 8 mm tape and reel -215 - -235
BC847A
BC847B
BC847B/DG
BC847C
BC847W SOT323 4 mm pitch, 8 mm tape and reel -115 - -135
BC847AW
BC847BW
BC847BW/DG
BC847CW
BC847T SOT416 4 mm pitch, 8 mm tape and reel -115 - -135
BC847AT
BC847AT/DG
BC847BT
BC847CT
BC847AM SOT883 2 mm pitch, 8 mm tape and reel - - -315
BC847BM
BC847CM
BC547 SOT54 bulk, straight leads - -412 -
BC547B
BC547C
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 12 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
[1] For further information and the availability of packing methods, see Section 12.
[2] /DG: halogen-free
BC547 SOT54A tape and reel, wide pitch - - -116
BC547B
BC547C
BC547 SOT54A tape ammopack, wide pitch - - -126
BC547B
BC547C
BC547 SOT54 variant bulk, delta pinning - -112 -
BC547B
BC547C
Table 9. Packing methods
…continued
The indicated -xxx are the last three digits of the 12NC ordering code.
[1]
Type number[2] Package Description Packing quantity
3000 5000 10000
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 13 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
10. Revision history
Table 10. Revision history
Document ID Release date Data sheet status Change notice Supersedes
BC847_BC547_SER_7 20081210 Product data sheet - BC847_BC547_SER_6
Modifications: •The format of this data sheet has been redesigned to comply with the new identity
guidelines of NXP Semiconductors.
•Legal texts have been adapted to the new company name where appropriate.
•Table 1 “Product overview”: enhanced
•Table 4 “Ordering information”: enhanced
•Table 5 “Marking codes”: enhanced
•Table 6 “Limiting values”: IEBO conditions amended
•Table 8 “Characteristics”: symbol N for parameter noise figure redefined to NF
•Table 9 “Packing methods”: enhanced
•Section 11 “Legal information”: updated
BC847_BC547_SER_6 20050519 Product data sheet - BC846_BC847_ BC848_5,
BC847M_SERIES_2,
BC846T_847T_ SERIES_3,
BC846W_BC847W_BC848W_4,
BC546_547_4
BC846_BC847_BC848_5 20040206 Product specification - BC846_BC847_ BC848_4
BC847M_SERIES_2 20040310 Product specification - BC847M_SERIES_1
BC846T_847T_SERIES_3 20001115 Product specification - BC846T_847T_2
BC846W_BC847W_
BC848W_4 20020204 Product specification - BC846W_847W_3
BC546_547_4 20041125 Product specification - BC546_547_3
BC847_BC547_SER_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 10 December 2008 14 of 15
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
11. Legal information
11.1 Data sheet status
[1] Please consult the most recently issued document before initiating or completing a design.
[2] The term ‘short data sheet’ is explained in section “Definitions”.
[3] The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status
information is available on the Internet at URL http://www.nxp.com.
11.2 Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Short data sheet — A short data sheet is an extract from a full data sheet
with the same product type number(s) and title. A short data sheet is intended
for quick reference only and should not be relied upon to contain detailed and
full information. For detailed and full information see the relevant full data
sheet, which is available on request via the local NXP Semiconductors sales
office. In case of any inconsistency or conflict with the short data sheet, the
full data sheet shall prevail.
11.3 Disclaimers
General — Information in this document is believed to be accurate and
reliable. However, NXP Semiconductors does not give any representations or
warranties, expressed or implied, as to the accuracy or completeness of such
information and shall have no liability for the consequences of use of such
information.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in medical, military, aircraft,
space or life support equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors accepts no liability for inclusion and/or use of
NXP Semiconductors products in such equipment or applications and
therefore such inclusion and/or use is at the customer’s own risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) may cause permanent
damage to the device. Limiting values are stress ratings only and operation of
the device at these or any other conditions above those given in the
Characteristics sections of this document is not implied. Exposure to limiting
values for extended periods may affect device reliability.
Terms and conditions of sale — NXP Semiconductors products are sold
subject to the general terms and conditions of commercial sale, as published
at http://www.nxp.com/profile/terms, including those pertaining to warranty,
intellectual property rights infringement and limitation of liability, unless
explicitly otherwise agreed to in writing by NXP Semiconductors. In case of
any inconsistency or conflict between information in this document and such
terms and conditions, the latter will prevail.
No offer to sell or license — Nothing in this document may be interpreted
or construed as an offer to sell products that is open for acceptance or the
grant, conveyance or implication of any license under any copyrights, patents
or other industrial or intellectual property rights.
Quick reference data — The Quick reference data is an extract of the
product data given in the Limiting values and Characteristics sections of this
document, and as such is not complete, exhaustive or legally binding.
11.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
12. Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: salesaddresses@nxp.com
Document status[1][2] Product status[3] Definition
Objective [short] data sheet Development This document contains data from the objective specification for product development.
Preliminary [short] data sheet Qualification This document contains data from the preliminary specification.
Product [short] data sheet Production This document contains the product specification.
NXP Semiconductors BC847/BC547 series
45 V, 100 mA NPN general-purpose transistors
© NXP B.V. 2008. All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: salesaddresses@nxp.com
Date of release: 10 December 2008
Document identifier: BC847_BC547_SER_7
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
13. Contents
1 Product profile . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 General description. . . . . . . . . . . . . . . . . . . . . . 1
1.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 Quick reference data. . . . . . . . . . . . . . . . . . . . . 2
2 Pinning information. . . . . . . . . . . . . . . . . . . . . . 2
3 Ordering information. . . . . . . . . . . . . . . . . . . . . 3
4 Marking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5 Limiting values. . . . . . . . . . . . . . . . . . . . . . . . . . 5
6 Thermal characteristics. . . . . . . . . . . . . . . . . . . 5
7 Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . 6
8 Package outline . . . . . . . . . . . . . . . . . . . . . . . . 10
9 Packing information. . . . . . . . . . . . . . . . . . . . . 11
10 Revision history. . . . . . . . . . . . . . . . . . . . . . . . 13
11 Legal information. . . . . . . . . . . . . . . . . . . . . . . 14
11.1 Data sheet status . . . . . . . . . . . . . . . . . . . . . . 14
11.2 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.3 Disclaimers. . . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.4 Trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 14
12 Contact information. . . . . . . . . . . . . . . . . . . . . 14
13 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
