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PFM19030 SPECIFICATION
1930-1990 MHz, 30W, 2-Stage Power Module Enhancement-Mode Lateral MOSFETs
This versatile PCS module provides excellent linearity and efficiency in a low-cost surface mount package. The PFM19030 includes two stages of Package Type: Surface Mount amplification, along with internal sense FETs that are on the same silicon PN: PFM19030SM die as the RF devices. These thermally coupled sense FETs simplify the task of bias temperature compensation of the overall amplifier. The module includes RF input, interstage, and output matching elements. The source and load impedances required for optimum operation of the module are much higher (and simpler to realize) than for unmatched Si LDMOS transistors of similar performance. The surface mount package base is typically soldered to a conventional PCB pad with an array of via holes for grounding and thermal sinking of the module. Optimized internal construction supports low FET channel temperature for reliable operation.
Package Type: Flange PN: PFM19030F
* 28 dB Gain * 30 Watts Peak Output Power * Internal Sense FETs (for improved bias control)
* IS95 CDMA Performance 5 Watts Average Output Level 20% Power Added Efficiency -49 dBc ACPR
Module Schematic Diagram
Module Substrate Q1 Die Carrier
Q1
Q2 Die Carrier
Q2
Drain 2 RF OUT
Output Match Lead
Gate 1 RF IN
Lead
Input Match
Output Match
Input Match
S1
S2
Sense S1 Gate 2
Lead
Lead
Sense S2
Lead
D1
Lead
Note: Additionally, there are 250 KOhm resistors connected in shunt with all leads, to enhance ESD protection.
Page 1 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Electrical Specification
Parameter Min
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Operating Frequency Gain Gain Compression at Pout =30 Watts Gain Flatness over any 30 MHz bandwidth Deviation from Linear Phase over any 30 MHz bandwidth Group Delay ACPR with IS95A CDMA Pave = 5 W Efficiency under IS-95 Protocol, Pave = 5 W Efficiency @ 30W CW Output DC Drain Supply Voltage Operating Temperature Range (base temperature) Gain Variation versus Temperature Output Mismatch Stress Stability Theta jc (channel) Quiescent Currents a) Q1 b) Q2 Sense FET Current/RF FET Current Ratio a) Stg 1 Sense b) Stg 2 Sense ESD Protection a) Human Body Model b) Machine Model 1930 27.0 -45 18
Limits Typ
29.0 0.8 0.2 0.8 3.1 -49 20.5 42
Units Max
1990 31.5 1.5 0.3 1.5 3.7 30 +115 30 2.1 MHz dB dB dB nanosec dBc % % Volts C dB/C Watts CW dBc C/W mA mA Note 1.
Comments
Pulsed CW compression measurement (12 sec pulse, 120 sec period, 10% duty cycle).
Includes delay of test fixture (~0.6 nanosec.). Note 3. Refer to applications data for performance with other protocols. Note 3.
24 -40 -60 -
27 -0.033 1.9 75 260
Testing for conformance with RF specifications is at +27 V. Testing for conformance with RF specification is at +25 C. Bias quiescent currents held constant. VSWR 10:1, all phase angles. No degradation in output power before & after test. 017
3.0 1.7
% %
18
Class 1 Class M3
Page 2 of 15
Specifications subject to change without notice. US Patent No.6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Electrical Specification (Continued)
MAXIMUM RATINGS
Rating
19 DC Drain Supply a) Drain-to-Source Voltage, (VGS=0), D1 & D2 & Track D1 & Track D2 b) Normal Operation (Class AB operation) DC Gate Supply a) Gate-to-source Voltage (VDS=0) Normal Operation (Class AB operation) RF Input Power Maximum Power Dissipation (T +85 C) a) Derate above +85 C base temperature. Maximum Channel Operating Temperature Storage Temperature Range
Symbol
VDS VD_SUPPLY VGS VG_SUPPLY PIN PTOTAL TCH TSTG
Value
+50 +30 -0.5Units
Volts DC Volts DC Volts DC Volts DC dBm Watts Watts/C C C
20 21 22 23 24
RECOMMENDED SOURCE AND LOAD IMPEDANCES
Impedance
Nominal Source Impedance for Optimum Operation Nominal Load Impedance for Optimum Operation 19 + j1.9
Units
Ohms
Comments
Matched for near-optimum linearity and gain flatness. Impedance is looking from the module input lead into the input matching circuit. Reference plane is 0.105 inches from the input end (case edge)of the module. Matched for near-optimum linearity under CDMA protocol. Impedance is from the module output lead looking into the output matching circuit. Reference plane is 0.105 inches from the output end (case edge) of the module.
21 + j6.3
Ohms
Specification Notes:
1) The module is mounted in a test fixture with external matching elements for all testing. Quiescent current bias conditions are those appropriate for minimum ACPR under CDMA protocol. Supply voltage for all tests is +27 volts DC. Testing is at +25 C unless otherwise specified. 2) Theta jc is measured with a package mounting (base) temp of +85 C, and with 10 Watts CW output. 3) Pout=5Watts average; IS-95A protocol: IS95 Forward Link PPS+ 9CH. ACPR conditions: a) 900 kHz offset, 30 kHz BW, b) 2.75 MHz offset, 1 MHz BW. 4) Sense FETs are scaled versions of the main RF FETs, formed from electrically isolated cells at end of the RF structure. Current scales according to periphery (threshold voltages offset is less than 150 millivolts between adjacent devices). RF & Sense FET gates and sources are DC connected. Drains are DC isolated. Leads S1 & S2 are DC connected to drains of sense FETs 1 & 2. Sources are connected to package base. Sense FETs are electrically isolated from the RF signals.
Page 3 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Typical Module Performance
T=+25 C, unless otherwise noted. Data is for module in a test fixture with external matching elements. See following page for test fixture details.
Typical Small-Signal Gain vs. Frequency
31 30 Gain (dB) 29 28 27
Gain & Efficiency vs. Output Power Pulsed Measurement, Vdc=+27V, F=1960 MHz
29 28 Gain (dB) 27 26 25 60% 50% 40% 30% 20% 10% 30 32 34 36 38 40 42 44 46 Ouptput Power (dBm) Efficiency
26 1840 1870 1900 1930 1960 1990 2020 2050 2080
24
Frequency (MHz)
Input and Output Return Loss vs Frequency.
0
Typical Output Power at 1 dB Gain Compression vs Freq. & Supply Voltage
47 Output Power (dBm) 46 45 44 43 1870 1900 1930 1960 1990 Frequency (MHz) 2020 2050
P1dB(+26V) P1dB(+27V) P1dB(+28V)
-2 Return Loss (dB) -4 -6 -8 -10 -12 -14 1900 1930 1960 Frequency (MHz) 1990 2020 INPUT OUTPUT
Typical S21 Phase Variation Versus Frequency (normalized about average insertion phase)
3
Typical CW Gain vs Swept CW Output Power, with Various Quiescent Bias Conditions
30 29
Bias for Best 2-Tone IMDs
2 Phase (degrees)
0 -1 -2
Gain (dB)
1
28 27 26 25
G(75/250 mA) G(68/225 mA) G(60/200 mA) G(82/275 mA)
-3 1930 1945 1960 Frequency (MHz) 1975 1990
24 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 CW Swept Output Power (dBm)
T
im
e
d
e la y
o
ffse t
=
3
.2
n
an
o
sec
( in
c lu
d
es
t im
e
d
e la y
o
f
te st
f ix
tu
re).
Note: This data illustrates the significance of quiescent bias current level. The unit was press mounted in the fixture & thermal effects are exagerated for this CW test.
Page 4 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Typical Module Performance
Typical CW 2-Tone Intermods vs. Output Power
Intermodulation Distortion (dBc) -10 -20 -30 -40 -50 -60 -70 30 31 32 33 34 35 36 37 38 39 40 Average Output Power (dBm) 41 42 43
IM3L IM3U IM5L IM5U IM7L IM7U
T=+25 C, unless otherwise noted. Data is for module in a test fixture with external matching elements. See following page for test fixture details.
Single-Signal IS95 CDMA ACPR & Efficiency vs Average Output Power (F=1960 MHz)
-20 -25 -30 ACPR (dBc) -35 -40 -45 -50 -55 -60 -65 -70 30
F1=1959.5 MHz, F2=1960.5 MHz Vsupply = +27 V, Idsq1 = 75 mA, Idsq2=250 mA
ACPR(-900 KHz) ACPR(+900 KHz) ACPR(-1.25 MHz) ACPR(+1.25 MHz) ACPR(-2.75 MHz) ACPR(+2.75 MHz) PAE (%)
30 27 24 18 15 12 9 6 3 0
Efficiency (%)
21
31
32 33 34 35 36 37 38 Average CDMA Output Power (dBm)
39
2-Tone IMD Rejection vs. Tone Separation (Peak Envelope Power = 44.5 dBm)
0 IM Rejection (dBc) -10 -20 -30 -40 -50 -60 0 10 20 30 40 50 CW Tone Separation (MHz)
IM3L IM3U IM5L IM5U IM7L IM7U
2 IS95 CDMA Signal IM Distortion vs. Ave Output Power (F=1955, 1965 MHz)
-20 -25 IM Rejection (dBc) -30 -35 -40 -45 -50 -55 -60 30 31 32 33 34 35 36 CDMA Total Average Power (dBm) 37 38
IM3(+15 MHz) IM3(-15 MHz) IM5(-25 MHz) IM5(+25 MHz)
F1=1930 MHz, F2=1930.5 MHz to 1980 MHz Vsupply = +27 V, Idsq1 = 75 mA, Idsq2=250 mA
WCDMA ACLR & Efficiency vs Output Power (F=1960 MHz, Test Model 1)
-15 -20 -25 ACLR (dBc) -30 -35 -40 -45 -50 30 31 32 33 34 35 36 37 38 Average WCDMA Output Power (dBm) 39
ACLR(-5 MHz) ACLR (+5 MHz) Efficiency
28 24 Efficiency (%) 20 16 12 8 4 0
Page 5 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Typical Module Performance
EDGE EVM & Efficiency vs. Pout
12 Error Vector Magnitude (%) 10
RMS EVM %
T=+25 C, unless otherwise noted. Data is for module in a test fixture with external matching elements. See following page for test fixture details.
30.0%
2-Tone 3rd Order IMD Rejection vs. Pout & First Stage Quiescent Bias Currents
-20
IM3(75/250) IM3(82/250) IM3(67/250) IM3(60/250) Idsq1=Opt-20% -10% +10% Idsq1=Optimum, 75 mA
25.0% Efficiency
-25 IMD Rejection (dBc)
Efficiency 20.0%
8
Efficiency
-30 -35 -40 -45 -50 -55
6 4 EVM 2 0 26 28 30 32 34 36 38 40 Average Output Power (dBm) 42 44
15.0% 10.0% 5.0% 0.0%
-60 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 Average Output Power (dBm)
EDGE ACPR vs. Average Pout
0 -10 -20 ACPR (dBc) -30 -40 -50 -60 -70 -80 36 37 38 39 40 41 Average Output Power (dBm) 42 43
lower 200khz upper 200khz lower 250khz upper 250khz lower 400khz upper 400khz lower 600khz upper 600khz lower 1.2mhz upper 1.2mhz
2-Tone 3rd Order IMD Rejection vs. Pout & Second Stage Quiescent Bias Currents
-20 -25 IMD Rejection (dBc) -30 -35 -40 -45 -50 -55 -60 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 Average Output Power (dBm)
-10% Idsq2 = Optimum, 250 mA +10% IM3(75/250) IM3(75/275) IM3(75/225) IM3(75/200) Idsq2=Optimum -20%
Page 6 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
PFM19030SM Package Outline
PFM19030F Package Outline
Page 7 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Module Application Notes
The PFM19030 was designed to provide a versatile low cost solution for a wide variety of wireless applications requiring 30 Watt peak output levels. This hybrid module contains two stages of Si LDMOS FET amplification: a nominally 5 Watt input stage driving a 30 Watt output stage. The module is optimized for efficient, linear operation with EDGE and CDMA signals. The input and output of this module are partially matched, and require source and load impedances of nominally 19 and 21 Ohms (much higher than typically required by unmatched Si LDMOS FETs). These source and load impedances can be achieved with compact conventional external PCB circuitry. Performance for particular signal protocols can be improved slightly by small adjustments in quiescent currents and load impedances presented to the module. The data presented in the previous pages was taken at one set of quiescent currents and in a fixture with source and load impedances that were fixed for all measurements. The data presented is generally representative of the performance - benefits from further optimization in quiescent current are small. In addition to the two RF gain stages, there are Sense FET (thermally tracking) devices that serve as optional DC circuit elements. The Sense FETs are fabricated on the same epi material with nominally identical physical characteristics (but smaller gate periphery) as the RF devices. The sense devices can be applied as temperature compensation elements in conjunction with external bias circuitry. Alternatively, the two-stage amplifier can be operated with the Sense FETs unused (S1 and S2 leads floating). The base of the module is high conductivity copper of 40 mil thickness. It is well matched to typical PCB material, and it serves as a heat spreader for the device when mounted as a surface-mount component. The module thermal characteristics were measured with the unit soldered to a 20 mil thick PCB material with an array of plated via holes for electrical grounding and thermal sinking. IR scans of this configuration demonstrated maximum die channel temperatures of 142 degrees C with a PCB base temperature of +95 degrees C, and 10 Watts CW output power. These modules can be provided in tape-and-reel configuration for high volume applications.
Typical PCB Mounting Pattern
The module outline is indicated by dashed line (0.60 X 1.00 inches). The ground pad is 1.030 X 0.630 inches. Ground vias in this example are 28 mil diameter on 35 mil (or 70 mil) centers. Thermal resistance is proportional to the thickness of the PC board (height of vias), and inversely proportional to the total ground hole array periphery (and thickness of plating in the holes). The densely spaced vias in this layout (on 35 mil spaces) are located in areas of maximum heat generation. The gap between the lead pads and the ground pad is 25 mils. Note that the underside of the PCB must be connected to a thermal heat sink and ground. The above hole pattern is an example of one that maximizes thermal transfer. There are numerous alternative approaches. Depending on the application (signal protocol, thermal environment, etc.), the number of via holes can be reduced. High average power applications require the most extensive thermal sinking. Page 8 of 15 Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/ Rev. 2
PFM19030
Recommended Passive Bias Circuit
This schematic demonstrates a method of applying the Sense FETs internal to the module that uses passive external circuitry. The circuit maintains a constant current through the Sense FETS, independent of temperature of the die. The Sense FETs are configured in this case as diodes. The temperature dependence of the Vf of the diode is very similar to that of the RF FET gate voltage, and therefore the quiescent current remains nearly constant over a wide temperature range. The advantage of this circuit is its simplicity and stability (avoidance of operational amplifiers) under all layout conditions. The main limitation of the circuit is that quiescent currents must be adjusted for each individual module (they are not easily pre-set with precision).
+10 to +20 V Gate
GND
+27 V
J1
8
7
6
5
4
3
2
1
Note: Typical Q1 diode bias = 1.4 mA (VG1 ~ 3.96V) Typical Q2 diode bias = 2.7 mA (VG2 ~ 4.21V) (based on 6/4/04 measurements)
C29 C28 C27
S1 C12 C11 C10 R6
S2
R5
C24 C22 C20
C23 C21 C19 C18 C17 C16 Drain 1 C15 R2 C9 C8 C7
C2 RF Out C1 RF OUT PFM19030
Sense D2 Gate 2 Sense D1 RF IN C4 C3 C5 R1
R3 RF Input
C6
Page 9 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Passive Bias Circuit Parts List
Designator
C2 C3 C5 C4 C6 C1, C7, C19, C20 C10, C13, C14, C15, C8, C11, C16, C21 C22 C23, C9, C17, C12 C24, C18 R5 R6 R1 R3 C27 C29 C28 S1, S2
Description
CAP, 1.2 PF0.1 pF, 0603, ATC 600S CAP, 2.0 PF0.1 pF, 0603, ATC 600S CAP, 1.8 PF0.1 pF, 0603, ATC 600S CAP, 4.7 PF0.1 pF, 0603, ATC 600S CAP, 3.0 PF0.1 pF, 0603, ATC 600S CAP, 27 PF5%, 0603, ATC 600S CAP, 27 PF5%, 100V (min), 0603, any vendor. CAP, 470 PF 10%,100 V, 0603, any vendor. CAP, 3300 PF10%, 100 V, 0603, Murata GRM39X7R332K100??, or equivalent. CAP, 15000 PF10%, 100 V, 0805, MurataGRM40X7R153K100??, or equivalent. CAP, 150000 1206, 50V, X7R, 10% Suggest Murata GRM42-6-X7R-154-K-050-A-L or equivalent. RES, potentiometer, 10Kohms, Digikey SM4W103-ND RES, potentiometer, 5 Kohms, Digikey SM4W502-ND RES, 1/16W, 0603, 1000 ohms, 5% RES, 1/16W, 0805, 124 Ohms, 5% CAP, 2.2uf SMT TANTALUM, 50V (240097) CAP, 10uf 16V SMT TANTALUM (240096) CAP, 47UF, 50V, ELECTR SMT (240087) SPST Switch, Digikey PN CKN1100CT-ND
Qty
1 1 1 1 1 4 4 4 1 4 2 1 1 1 1 1 1 1 2
Page 10 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Test Fixture
A metal-backed PCB with clamps for securing the module is used for module electrical testing and for product demonstration. The fixture is supplied mounted to a finned heat sink. The fixture schematic is provided on the following page.
This test fixture uses an active bias circuit, which sets the bias circuit through the Sense FETs (configured as FETs) and applies the derived gate voltage to the associated RF FETs. This assures particular quiescent bias currents, with accuracy determined by the Sense FET-to-RF FET current ratios.
Page 11 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Test Fixture Schematic
GND +27 V +27 V OpAmp
J2 Not Used for Demo Fixture
J1
8
7
6
5
4
3
2
1
J2
8 7 6 5 4 3 2 1 RZ_FS1 RZ_FS2
C31 R12 R11 C32 R16 R13 4 5 U1
C37 R32 R31
C34 C36 R36 R33 4
C40
R14 C33
LM8261 1 + 3 2 R19 R15
C42 C41 R20 R37 R34 C35
5 LM8261 + 3 2 R35
U2
C43
R39
R40
R38 S2 D2
R17 R18 S1 D1
C28
C27
C26
C12 C11 C10 C25
C24 C22 C20
C23 C21 C19 C18
C14
C9 C17 C16 Drain 1 C15 C8 C7
C2 RF Out C1 RF OUT PFM19030SM
Sense D2 Gate 2 Sense D1 RF IN C4 C3 C5 R1
R2 RF Input
C6
See the following pages for the parts list and a description of the principle of operation. Note that an alternative, less complex bias scheme is provided later in this applications note. The advantage of the above bias design is that bias currents are set by the RF-to-Sense FET ratios, and once the optimum bias circuit resistor (potentiometer) values are established, the circuit can stay fixed for multiple modules (thus eliminating module-specific bias alignment). Additionally, aging effects are minimized because of the Page 12 of 15 Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/ Rev. 2
PFM19030
similar bias conditions for Sense and RF FETs. The disadvantage of this design is its relative complexity and the incorporation of operational amplifiers, for which stability is potentially circuit layout dependent.
Parts List for Cree Microwave Test Fixture
Designator
C2 C3 C5 C4 C6 C1, C7, C19, C20 C10, C13, C14, C15, C8, C11, C16, C21 C22 C9, C23, C17, C12 C18, C24, C25, C26, C31, C34 C27, C37 C28 C33, C35 C32, C36 C40, C41, C42, C43 R1 R2 R11, R12 R31, R32 R13, R14, R33, R34 R16, R15, R35, R36 R19, R39 R18 R38 R20, R40 R17, R37 RZ_FS1, RZ_FS2 D1, D2 S1, S2 U1, U2
Description
CAP, 1.2 PF0.1 pF, 0603, ATC 600S CAP, 2.0 PF0.1 pF, 0603, ATC 600S CAP, 1.8 PF0.1 pF, 0603, ATC 600S CAP, 4.7 PF0.1 pF, 0603, ATC 600S CAP, 3.0 PF0.1 pF, 0603, ATC 600S CAP, 27 PF5%, 0603, ATC 600S CAP, 27 PF5%, 100V (min), 0603, any vendor. CAP, 470 PF 10%,100 V, 0603, any vendor. CAP, 3300 PF10%, 100 V, 0603, Murata GRM39X7R332K100 CAP, 15000 PF10%, 100 V, 0805, MurataGRM40X7R153K100 CAP, 150000 1206, 50V, X7R, 10% Murata GRM42-6-X7R-154-K-050-A-L CAP, 2.2uf SMT TANTALUM, 50V CAP, 47UF, 50V, ELECTR SMT CAP, 18,000 PF 10%,100 V, 0603 CAP, 33,000 PF 10%,100 V, 0603 CAP, 1000 PF 10%,100 V, 0603. RES, 1/16W, 0603, 1000 ohms, 5% RES, 1/16W, 0805, 124 Ohms, 5% RES, 1/16W, 0603, 332 Ohms, 1% RES, 1/16W, 0603, 147 Ohms, 1% RES, 1/16W, 0603, 2370 Ohms, 1% RES, 1/16W, 0603, 511 KOhms, 1% RES, 1/16W, 0603, 100 KOhms, 5% RES, 1/16W, 0603, 3320 Ohms, 5% RES, 1/16W, 0603, 2000 Ohms, 5% RES, 1/8W, 1206, 1000 Ohms, 5% RES, potentiometer, 10 Kohms, Digikey SM4W103-ND, 11T RES, 1/16W, 0805, 0 Ohms (used as jumpers, demo fixture only) Zener diode, 6.2 V, Digikey PN BZT52C6V27DICT-ND SPST Switch, Digikey PN CKN1100CT-ND Op Amp, High Output, LM8261M5 (5 pin, SOT23 package)
Qty
1 1 1 1 1 4 4 4 1 4 6 2 1 2 2 4 1 1 2 2 4 4 2 1 1 2 2 2 2 2 2
It is also possible to bias the two stages in a conventional manner, with the two tracking FET drains left unused (floating or grounded). The above bias circuits are just two of several possibilities.
Page 13 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2
PFM19030
Test Fixture Active Bias Circuit Principles of Operation
The test fixture operates off of a single voltage supply. It contains two switches and two potentiometers. The switches provide for independent on/off for the input and output devices of the module. The potentiometers allow adjustment of quiescent current level of each stage. The adjustments should be made with no RF applied to the module.
Q1 Die Carrier
Q1
Input Match Output Match
Vsupply S1 R1 <+
Differental Amp
Ids_sense Rbias
Ireference
Principal of Operation of Bias Circuitry The principal of operation of the fixture bias circuit is demonstrated in the above Figure. The potentiometer establishes a reference current, and the operational amplifier adjusts gate voltage to maintain that current in the sense device. The same DC gate voltage is also applied to the main (RF) device. Sense devices are scaled versions of the main (RF) devices, on the same die (to facilitate temperature tracking). As the temperature of the die changes due to RF drive (or ambient temperature changes), the operational amplifier maintains constant current through the Sense FET, and thus constant quiescent bias for the main (RF) FET. No RF signal is applied to the Sense FET. There is a separate independent bias circuit for the input (Q1) device and for the output device (Q2) of the module. Experience has shown this bias circuit to be a reliable method of maintaining tight control of quiescent current over operating temperature, and for minimizing the impact of device aging effects on amplifier performance. However, there are some precautions regarding use of this circuit. The principle of the circuit is for the differential amplifier (op amp) to adjust gate voltage until the desired current is achieved through the sense FETs. If the current path is interrupted (thereby not allowing Ids_sense to flow), the operational amplifier will increase gate bias in an attempt to increase current, with the possibility that the quiescent bias current in the RF FET may increase beyond a safe limit (the device may be destroyed). The zener diodes in the test fixture circuit (D1 and D2, test fixture schematic) are safeguards for prohibiting excessive gate voltage to be applied to the transistors. Page 14 of 15 Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/ Rev. 2
PFM19030
Disclaimer: Specifications are subject to change without notice. Cree Microwave, Inc. believes the information contained within this data sheet to be accurate and reliable. However, no responsibility is assumed by Cree Microwave for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Cree Microwave. Cree Microwave makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose. "Typical" parameters are the average values expected by Cree Microwave in large quantities and are provided for information purposes only. These values can and do vary in different applications, and actual performance can vary over time. All operating parameters should be validated by customer's technical experts for each application. Cree Microwave products are not designed, intended, or authorized for use as components in applications intended for surgical implant into the body or to support or sustain life, in applications in which the failure of the Cree product could result in personal injury or death, or in applications for planning, construction, maintenance or direct operation of a nuclear facility. Cree Microwave is a trademark and Cree and the Cree logo are registered trademarks of Cree, Inc.
Contact Information: Cree Microwave, Inc. 160 Gibraltar Court Sunnyvale, CA 94089-1319 Sheryle Henson (Cree Microwave--Marketing Manager) 408-962-7783 Tom Dekker (Cree Microwave--Sales Director) 919-313-5639
Page 15 of 15
Specifications subject to change without notice. U.S. Patent No. 6,822,321 http://www.cree.com/
Rev. 2

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