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MAX2602
(Rev.:2008)

3.6V, 1W RF Power Transistors for 900MHz Applications

Maxim Integrated 

3.6V, 1W RF Power Transistors

for 900MHz Applications

VBB

0.1μF

RFIN

2pF

1000pF

5Ω

100nH

24Ω

4

1000pF

5

T1

12pF

L1 = COILCRAFT A05T INDUCTOR, 18.5nH

T1, T2 = 1", 50Ω TRANSMISSION LINE ON FR-4

1000pF

L1

0.1μF

1

1000pF

8

T2

10pF

2, 6, 7

BACKSIDE

SLUG

VCC

2pF

Figure 1. Test Circuit

_______________Detailed Description

MAX2601/MAX2602

The MAX2601/MAX2602 are high-performance silicon

bipolar transistors in power-enhanced, 8-pin SO pack-

ages. The base and collector connections use two pins

each to reduce series inductance. The emitter connects

to three (MAX2602) or four (MAX2601) pins in addition

to a back-side heat slug, which solders directly to the

PC board ground to reduce emitter inductance and

improve thermal dissipation. The transistors are intend-

ed to be used in the common-emitter configuration for

maximum power gain and power-added

efficiency.

Current Mirror Bias

(MAX2602 only)

The MAX2602 includes a high-performance silicon

bipolar RF power transistor and a thermally matched

biasing diode that matches the power transistor’s ther-

mal and process characteristics. This diode is used to

create a bias network that accurately controls the

power transistor’s collector current as the temperature

changes (Figure 2).

The biasing diode is a scaled version of the power tran-

sistor’s base-emitter junction, in such a way that the

current through the biasing diode is 1/15 the quiescent

collector current of the RF power transistor. Supplying

the biasing diode with a constant current source and

connecting the diode’s anode to the RF power transis-

tor’s base ensures that the RF power transistor’s quies-

cent collector current remains constant through

VCC

VCC

RBIAS

RFC

Q1

CBIAS

CIN

RFIN

RFC

COUT

Q2

RFOUT

Figure 2. Bias Diode Application

temperature variations. Simply tying the biasing diode

to the supply through a resistor is adequate in most sit-

uations. If large supply variations are anticipated, con-

nect the biasing diode to a reference voltage through a

resistor, or use a stable current source. Connect the

biasing diode to the base of the RF power transistor

through a large RF impedance, such as an RF choke

(inductor), and decouple to ground through a surface-

mount chip capacitor larger than 1000pF.

4 _______________________________________________________________________________________

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