Philips AN10714 Application note

AN10714

Using the BLF574 in the 88 MHz to 108 MHz FM band

Rev. 01 — 26 January 2010 Application note

Document information

Info Content Keywords BLF574, 600 MHz performance, high voltage LDMOS, amplifier

implementation, Class-B CW, FM band, pulsed power

Abstract This application note describes the design and the performance of the

BLF574 for Class-B CW and FM type applications in the 88 MHz to 108 MHz frequency range.

NXP Semiconductors

AN10714

Using the BLF574 in the 88 MHz to 108 MHz FM band

Revision history

Rev Date Description

01 20100126 Initial version

Application note Rev. 01 — 26 January 2010 2 of 21

NXP Semiconductors

1. Introduction

The BLF574 is a new, 50 V, push-pull transistor using NXP Semiconductors’ 6th generation of high voltage LDMOS technology. The two push-pull sections of the device are completely independent of each other inside the package. The gates of the device are internally protected by the integrated ElectroStatic Discharge (ESD) diode.

The device is unmatched and is designed for use in applications below 600 MHz where very high power and efficiency are required. Typical applications are FM/VHF broadcast, laser or Industrial Scientific and Medical (ISM) applications.

Great care has been taken during the design of the high voltage process to ensure that the device achieves high ruggedness. This is a critical parameter for successful broadcast operations. The device can withstand greater than a 10 full operating power.

Another design goal was to minimize the size of the application circuit. This is important in that it allows amplifier designers to maximize the power in a given amplifier size. The design highlighted in this application note achieves over 600 W in the 88 band in a space smaller than 50.8 as wide as the transistor itself, enabling transistor mounting in the final amplifier to be as close as physically possible while still providing adequate room for the circuit implementation.

AN10714

Using the BLF574 in the 88 MHz to 108 MHz FM band

: 1 VSWR for all phase angles at

MHz to 108 MHz

mm × 101.6 mm (2 ” × 4 ”). The circuit only needs to be

This application note describes the design and the performance of the BLF574 for Class-B CW and FM type applications in the 88

MHz to 108 MHz frequency band.

Application note Rev. 01 — 26 January 2010 3 of 21

NXP Semiconductors

2. Circuit diagrams and PCB layout

2.1 Circuit diagrams

AN10714

Using the BLF574 in the 88 MHz to 108 MHz FM band

C27

C26C25

RF in

V bias in

R12

L22

R8 R3

C6 C5

R15 R14 R10

R11

R16

L10

L24

C30

C29C28

R13

L11

001aal30

Fig 1. BLF574 input circuit schematic; 88 MHz to 108 MHz

Application note Rev. 01 — 26 January 2010 4 of 21

NXP Semiconductors

AN10714

Using the BLF574 in the 88 MHz to 108 MHz FM band

C17 C18 C19 C20

L14

L25

L15

C21

C12

L23

C31

C32

C33

C34

L12

C13

C22 C23

L16

L17

C24

C15

C16

C10

L12

L13

C11

Fig 2. BLF574 output circuit schematic; 88 MHz to 108 MHz

C14

L19

L20

RF out

L21

001aal30

Application note Rev. 01 — 26 January 2010 5 of 21

Application note Rev. 01 — 26 January 2010 6 of 21

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NXP Semiconductors

2.2 BLF574 PCB layout

C20

C25

D1C6R8 C5

L22

R9 C7

BLF574

input-rev 3

30RF35

C26

R10R12 C29

C27

R11

C28

C30

R13

R16

L14

L10

L24

L11

R15

R14

C10 C15

L12

L13

C16 C11

L15

BLF574

output-rev 3

30RF35

L23

C12

L16

C13

C31

C32

C33

C34

L17

L18

C17 C18 C19

C14

C21 C22 C23

L19

L20

L21

Using the BLF574 in the 88 MHz to 108 MHz FM band

C24

001aal30

AN10714

The positions of C1, C19 and C23 are indicated but these capacitors are not connected.

Fig 3. BLF574 PCB layout

NXP Semiconductors

AN10714

Using the BLF574 in the 88 MHz to 108 MHz FM band

2.3 Bill Of Materials

Table 1. Bill of materials for the BLF574 input and output circuits

PCB material: Taconic RF35;

Designator Description Part number Manufacturer

B1 63.5 mm (2.5 ”)/50 Ω semirigid through

B2 coax cable; 124.5 mm (4.9 ”)/50 Ω;

C1 not connected - C2, C3 4700 pF ceramic chip capacitor ATC700B472KW50X American Technical Ceramics C4, C7, C26, C29 1 μF ceramic chip capacitor GRM31MR71H105KA88L MuRata C5, C6, C9 100 nF ceramic chip capacitor GRM21BR71H104KA01L MuRata C8 620 pF ceramic chip capacitor ATC100B621JT100X American Technical Ceramics C10, C11 390 pF ceramic chip capacitor ATC100B220GT500X American Technical Ceramics C12, C13 180 pF ceramic chip capacitor ATC100B181JT200X American Technical Ceramics C14 6.8 pF ceramic chip capacitor ATC100B6R8CT500X American Technical Ceramics C15, C16 15 pF ceramic chip capacitor ATC100B150JT500X American Technical Ceramics C17, C21, C31, C32 100 nF/250 V ceramic chip capacitor GRM32DR72E104KW01L MuRata C18, C22, C33, C34 2.2 μF/100 V ceramic chip capacitor GRM32ER72A225KA35 MuRata C19, C23 not connected - C20, C24 1000 μF, 100 V electrolytic capacitor EEV-TG1V102M Panasonic C25, C28 10 nF/35 V ceramic chip capacitor GRM32ER7YA106KA12L MuRata C27, C30 100 nF ceramic chip capacitor GRM31CR72E104KW03L MuRata D1 LED APT2012CGCK KingBright L1 21.7 mm × 1.75 mm (855 mil × 69 mil) - L2 9.2 mm × 1.65 mm (364 mil × 65 mil) - L3 9.9 mm × 1.75 mm (390 mil × 69 mil) - L4, L5 6.2 mm × 5.5 mm (243 mil × 218 mil) - L6, L7 L8, L9 5.2 mm × 5.54 mm (205 mil × 218 mil) - L10, L11 13.0 mm × 13.2 mm (511 mil × 520 mil) - L12, L13 8.8 mm × 13.2 mm (345 mil × 520 mil) - L14, L15 8.83 mm × 3.81 mm (348 mil × 150 mil) - L16, L17 L18, L23 3 turns 14 gauge wire;

L19 21.2 mm × 1.75 mm (834 mil × 69 mil) - L20 9.5 mm × 1.82 mm (373 mil × 72 mil) - L21 13.99 mm × 1.7 mm (551 mil × 65 mil) - L22 ferroxcube bead 2743019447 Fair Rite L24 50.8 mm (2 ”); 14 gauge wire;

L25 7.6 mm × 15.3 mm (299 mil × 604 mil) - -

= 3.5; thickness 0.76 mm (30 mil). Figure 3 shows the BLF574 PCB layout.

[1]

ferrite

ID = 3.5814 mm (0.141 ")

[2]

ID = 7.9 mm (0.310 ”)

ID = 15.5 mm (0.61 ”)

[3]

ferrite: BN-61-202 Amidon semirigid: 047-50 Micro-Coax UT-141C-Form-F Micro-Coax

- -

Application note Rev. 01 — 26 January 2010 7 of 21

+ 14 hidden pages

Philips AN10714 Application note

Specifications and Main Features

Frequently Asked Questions

User Manual

1. Introduction

2. Circuit diagrams and PCB layout

2.1 Circuit diagrams

2.2 BLF574 PCB layout

2.3 Bill Of Materials