AH128-89PCB1960 - TriQuint Semiconductor

Specifications and information are subject to change without notice

TriQuint Semiconductor Inc • Phone 1-503-615-9000• FAX: 503-615-8900 • e-mail: info- s ales@tqs.com • Web site: www.TriQuint.com Page 1 of 8 Aug 2009

AH128

¼W High Linearity InGaP HBT Amplifier

Product Features

• 60 – 3500 MHz

• +24.6 dBm P1dB

• +41.5 dBm Output IP3

• 16.6 dB Gain @ 2140 MHz

• 115 mA current draw

• +5V Single Supply

• MTTF > 100 Years

• Lead-free/Green/RoHS-compliant

SOT-89 Package

Applications

• Repeaters

• Mobile Infrastructure

• WiMAX / WiBro

• LTE / WCDMA / EDGE / CDMA

Product Description

The AH128 is a high dynamic range driver amplifier in a

low-cost surface mount package. The InGaP/GaAs HBT is

able to achieve high performance across a broad range with

+41.5 dBm OIP3 and +24.6 dBm of compressed 1dB

power while drawing 115 mA current. The AH128 is

available in a lead-free/green/RoHS-compliant SOT-89

package. All devices are 100% RF and DC tested.

The AH128 is targeted for use as a driver amplifier in

wireless infrastructure where high linearity, medium power,

and high efficiency are required. Internal biasing allows

the AH128 to maintain high linearity over temperature and

operate directly off a single +5V supply. This combination

makes the device an excellent candidate for transceiver line

cards in current and next generation multi-carrier 3G base

stations.

Functional Diagram

RF IN GND RF OUT

GND

1 23

Function Pin No.

RF Input 1

RF Output / Vcc 3

Ground 2, 4

Specifications

Parameter Units Min Typ Max

Operational Bandwidth MHz 60 3500

Test Frequency MHz 2140

Gain dB 14.5 16.6 19

Input Return Loss dB 13

Output Return Loss dB 10

W-CDMA Channel Power(2)

-50 dBc ACLR, 2140 MHz dBm +14.6

Output P1dB dBm +24.6

Output IP3(4) dBm +41.5

Noise Figure dB 4.4

Quiescent Collector Current mA 95 115 130

Device Voltage V +5

1. Test conditions unless otherwise noted: 25ºC, Vsupply = +5 V, in tuned application circuit.

2. W-CDMA 3GPP Test Model 1+64 DPCH, PAR = 9.7 dB @ 0.01% Probability, 3.84 MHz BW

3. IS-95A, 9 channel Fwd, PAR = 9.7 dB @ 0.01% Probability , 1.23 MHz BW.

4. OIP3 is measured with two tones separated by 1 MHz. The suppression on the largest IM3 product

is used to calculate the OIP3 using a 2:1 rule. Measured at 13 dBm/tone for 900 MHz & 1960 MHz

and 10 dBm/tone for 2140 MHz.

Absolute Maximum Rating

Parameter Rating

Storage Temperature -65 to +150 °C

RF Input Power, CW, 50 Ω, T=25°C Input P10dB

Device Voltage +6 V

Max Junction Temperature, TJ

For 106 hours MTTF 200 °C

Thermal Resistance, ΘJC 116 °C / W

Operation of this device above any of these parameters may cause permanent damage.

Typical Performance

Parameter Units Typical

Frequency MHz 920 1960 2140

Gain dB 19.5 17.2 16.6

Input Return Loss dB 14 14 13

Output Return Loss dB 7.8 11 10

IS-95A Channel Power(3)

-50 dBc ACPR dBm +17.5

W-CDMA Channel Power(2)

-50 dBc ACLR dBm +15.3 +15.5 +14.6

Output P1dB dBm +24.6 +24.8 +24.6

Output IP3(4) dBm +40 +40.8 +41.5

Noise Figure dB 4.6 4.5 4.4

Quiescent Collector Current mA 115

Device Voltage V +5

Ordering Information

Part No. Description

AH128-89G ¼ W High Linearity InGaP HBT Amplifier

AH128-89PCB900 900 MHz Evaluation Board

AH128-89PCB1960 1960 MHz Evaluation Board

AH128-89PCB2140 2140 MHz Evaluation Board

Standard T/R size = 1000 pieces on a 7” reel.

Specifications and information are subject to change without notice

TriQuint Semiconductor Inc • Phone 1-503-615-9000• FAX: 503-615-8900 • e-mail: info- s ales@tqs.com • Web site: www.TriQuint.com Page 2 of 8 Aug 2009

AH128

¼W High Linearity InGaP HBT Amplifier

Typical Device Data

S-Parameters (VDevice = +5 V, ICC = 115 mA, 25 °C, unmatched 50 ohm system)

Notes:

The gain for the unmatched device in 50 ohm system is shown as the trace in black color. For a tuned circuit for a particular frequency, it is expected that

actual gain will be higher, up to the maximum stable gain. The maximum stable gain is shown in the dashed red line.

S-Parameters (VDevice = +5 V, ICC = 115 mA, 25 °C, unmatched 50 ohm system, calibrated to device leads)

Freq (MHz) S11 (dB ) S11 (ang) S21 (dB) S21 (ang) S12 (dB) S12 (ang) S22 (dB) S22 (ang)

50 -5.38 -173.57 22.87 166.30 -30.49 4.94 -12.66 -146.31

100 -4.89 -176.21 21.96 165.00 -30.37 2.12 -11.24 -162.50

300 -4.91 -175.57 21.84 151.04 -30.66 -0.34 -11.69 -161.87

500 -3.95 -175.05 21.01 130.39 -30.54 1.26 -9.18 -156.72

700 -3.10 -179.25 19.51 114.04 -30.06 -1.57 -7.38 -162.95

900 -2.51 175.19 18.02 102.07 -29.47 -3.23 -6.59 -171.09

1100 -2.25 170.64 16.77 92.59 -29.27 -7.07 -6.09 -178.21

1300 -2.12 165.24 15.56 84.05 -29.04 -9.77 -5.69 175.48

1500 -2.01 160.47 14.47 76.48 -28.75 -12.83 -5.57 170.50

1700 -2.01 156.16 13.46 69.77 -28.78 -16.94 -5.59 165.41

1900 -1.92 150.48 12.74 63.07 -28.52 -20.19 -5.46 159.78

2100 -1.84 145.43 11.87 56.47 -28.43 -24.12 -5.36 154.06

2300 -1.76 141.16 11.08 50.21 -28.64 -26.71 -5.26 150.23

2500 -1.73 137.11 10.51 45.46 -28.47 -29.12 -5.54 146.96

2700 -1.69 131.81 10.11 39.00 -28.22 -33.92 -5.63 140.38

2900 -1.74 127.64 9.60 33.91 -27.96 -37.08 -5.41 135.33

3100 -1.83 121.13 9.17 27.49 -28.09 -40.84 -5.37 131.92

3300 -1.90 115.79 8.52 22.19 -28.02 -43.96 -5.63 129.40

3500 -1.90 112.40 8.12 16.48 -28.00 -46.34 -5.73 121.96

Device S-parameters are available for download off of the website at: http://www.tqs.com

Application Circuit PCB Layout

Circuit Board Material: 0.014” FR4, single layer, 1 oz copper,

r =

4.3, Microstrip line details: width = .031”, spacing = .035”

Specifications and information are subject to change without notice

TriQuint Semiconductor Inc • Phone 1-503-615-9000• FAX: 503-615-8900 • e-mail: info- s ales@tqs.com • Web site: www.TriQuint.com Page 3 of 8 Aug 2009

AH128

¼W High Linearity InGaP HBT Amplifier

700-800 MHz Application Circuit Performance Plots

802.16-2004 O-FDMA, 64QA M-1/2, 1024-FFT, 20 sy mbols and 30 subchannels, 5 MH z Carrier B W

Typical O-FDMA Performance at 25°C

Frequency (MHz) 700 750 800 Units

Gain 20.9 20.7 20.4 dB

Input Return Loss 15.7 19.6 16 dB

Output Return Loss 8.9 7.6 6.6 dB

EVM

Pout=+16 dBm 1.8 1.6 1.5 %

Output P1dB +24.3 +24.4 +24.6 dBm

Output IP3

Pout=+15 dBm/tone, 1MHz spacing +38.5 +39.7 +40.2 dBm

Quiescent Current, Icq 115 mA

Vcc +5

C10

L2 R2

Notes:

1. The primary RF microstrip line is 50 Ω.

2. Components shown on the silkscreen but not on the schematic are not used.

3. 0 Ω jumpers can be replaced with copper trace in target application.

4. The edge of R1 is placed 105 mil from the AH128 RFin pin. (4.4o @ 750 MHz)

5. The edge of L2 is placed 40 mil from the edge of R1. (1.7o @ 750 MHz)

6. The edge of L3 is placed 135 mil from the AH128 RFout pin. (5.6o @ 750 MHz)

7. The edge of C9 is placed 75 mil from the edge of L3. (3.1o @ 750 MHz)

Gain vs. Frequency

T=25°C

700 720 740 760 780 800

Frequency (MHz)

Gain (dB)

Return Loss

T=25°C

-30

-25

-20

-15

-10

-5

700 720 740 760 780 800

Frequency (GHz)

S11, S22 (dB)

S11 S22

EVM vs. Output Average Power vs. Frequency

T=25°C

14 15 16 17 18 19

Output Power (dBm)

EVM (%)

700 MHz 750 MHz 800 MHz

802.16-2004 O-FDMA, 64QAM-1/2,

1024-FFT, 20 symbols and 30

subchannels, 5 MHz Carrier BW

Current vs Output Average Power vs. Frequency

T=25°C

100

120

140

160

180

14 15 16 17 18 19

Output Power (dBm)

Collector Current (mA)

700 MHz 750 MHz 800 MHz

802.16-2004 O-FDMA, 64QAM-1/2,

1024-FFT, 20 symbols and 30

subchannels, 5 MHz Carrier BW

ACLR vs. Output Average Power vs. Frequency

T=25°C

-60

-55

-50

-45

-40

-35

10 12 14 16 18 20

Output Power (dBm)

ACLR (dBc)

700 MHz 750 MHz 800 MHz

W-CDMA 3GPP Test M odel 1+64 DPCH

PAR = 9.7 dB @ 0.01% Probability

3.84 MHz BW

OIP3 vs. Output Power /Tone vs. Frequency

T=25°C

8 1012141618

Output Power/Tone (dBm)

OIP3 (dBm)

700 MHz 750 MHz 800 MHz

Specifications and information are subject to change without notice

TriQuint Semiconductor Inc • Phone 1-503-615-9000 • FAX: 503-615-8900 • e-mail: info-s ales@tqs.com • Web site: www.TriQuint.com Page 4 of 8 Aug 2009

AH128

¼W Hi

h Linearit

InGaP HBT Am

lifier

869-960 MHz Reference Design (AH128-89PCB900)

IS-95A, 9 channel Fwd, PAR = 9.7 dB @ 0.01% Probability

Typical IS-95A Performance at 25°C

Frequency (MHz) 869 920 960 Units

Gain 19.7 19.5 19.4 dB

Input Return Loss 12 14 15 dB

Output Return Loss 8.2 7.8 7.3 dB

ACPR

Pout=+16 dBm -54 -55 -55 dBc

Output P1dB +24.4 +24.6 +24.5 dBm

Output IP3

Pout=13dBm/tone, 1MHz spacing +39 +40 +41 dBm

Noise Figure 4.7 4.6 4.7 dB

Quiescent Current, Icq 115 mA

Vcc +5 V

Notes:

1. The primary RF microstrip line is 50 Ω.

2. Components shown on the silkscreen but not on the schematic are not used.

3. 0 Ω jumpers can be replaced with copper trace in target application.

4. The edge of R2 is placed at 285mil from AH128 RFout pin. (14o @ 920 MHz)

5. The edge of C9 is placed against the edge of R2.

6. The edge of R1 is placed at 100mil from AH128 RFin pin. (5o @ 920 MHz)

7. The edge of C10 is placed 260mil from the edge of R1. (13o @ 920 MHz)

Gain vs. Frequency

T=25°C

0.84 0.86 0.88 0.90 0.92 0.94 0.96 0.98

Frequency (GHz)

Gain (dB)

Return Loss

T=25°C

-25

-20

-15

-10

-5

0.84 0.86 0.88 0.90 0.92 0.94 0.96 0.98

Frequency (GHz)

S11, S22 (dB)

S11 S22

OIP3 vs. Output Power/Tone vs. Temperature

f=920 MHz

7 9 11 13 15 17 19

Output Power/Tone (dBm)

OIP3 (dBm)

+25°C -40°C +85°C

ACPR vs. Output Average Power vs. Frequency

T=25°C

-80

-75

-70

-65

-60

-55

-50

-45

-40

10 12 14 16 18

Output Power (dBm)

ACPR (dBc)

869 MHz 920 MHz 960 MHz

IS-95A, 9 cha nnel Fwd

PAR=9.7@0.0 1% Pr ob ab il ity

ACPR vs. Output Average Power vs. Temperature

f=920 MHz

-80

-75

-70

-65

-60

-55

-50

-45

-40

10 12 14 16 18

Output Power (dBm)

ACPR (dBc)

+25°C -40°C +85°C

IS-95A, 9 channel Fwd

PAR=9.7@0. 01% Probabilit y

OIP3 vs . Output Power/Tone vs. Frequency

T=25°C

7 9 11 13 15 17 19

Output Power/Tone (dBm)

OIP3 (dBm)

869 MHz 920 MHz 960 MHz

NF vs. Frequency

T=25°C

0.90 0.92 0.94 0.96 0.98

Frequency (GHz)

NF (dB)

Current vs O utp ut Av erag e Power v s. Freque ncy

T=25°C

100

120

140

160

180

200

12 14 16 18 20 22 24

Output Power (dBm)

Collector Current (mA)

869 MHz 920 MHz 960 MHz

ACLR vs. O utpu t Av erage Power v s. Fre quency

T=25°C

-70

-65

-60

-55

-50

-45

-40

-35

-30

10 12 14 16 18

Output Power (dBm)

ACLR (dBc)

869 MHz 920 MHz 960 MHz

W-CDMA 3GPP Test Model 1+64 DPCH

PAR = 9.7 dB @ 0.01% Probability

3.84 MHz BW

Specifications and information are subject to change without notice

TriQuint Semiconductor Inc • Phone 1-503-615-9000 • FAX: 503-615-8900 • e-mail: info-s ales@tqs.com • Web site: www.TriQuint.com Page 5 of 8 Aug 2009

AH128

¼W Hi

h Linearit

InGaP HBT Am

lifier

1930-1990 MHz Reference Design (AH128-89PCB1960)

W-CDMA 3GPP Test Model 1+64 DPCH, PAR = 9.7 dB @ 0.01% Probability, 3.84 MHz BW

Typical W-CDMA Performance at 25°C

Frequency (MHz) 1930 1960 1990 Units

Gain 17.3 17.2 17.1 dB

Input Return Loss 13 14 15 dB

Output Return Loss 11 11 10 dB

ACLR

Pout=+15 dBm -52 -51 -51.5 dBc

Output P1dB +24.8 +24.8 +24.8 dBm

Output IP3

Pout=13dBm/tone, 1MHz spacing +40.9 +40.8 +40.4 dBm

Noise Figure 4.4 4.5 4.6 dB

Quiescent Current, Icq 115 mA

Vcc +5 V

Notes:

1. The primary RF microstrip line is 50 Ω.

2. Components shown on the silkscreen but not on the schematic are not used.

3. 0 Ω jumpers can be replaced with copper trace in target application.

4. The edge of C9 is placed at 265mil from AH128 RFout pin. (29 o @ 1960 MHz)

5. The edge of R2 is placed against the edge of C9.

6. The edge of R1 is placed at 100mil from AH128 RFin pin. (11 o @ 1960 MHz)

7. The edge of C10 is placed 220mil from the edge of R1. (24 o @ 1960 MHz)

Gain vs. F requency

T=25°C

1.92 1.94 1.96 1.98 2.00

Frequency (GHz)

Gain (dB)

Return Loss

T=25°C

-25

-20

-15

-10

-5

1.92 1.94 1.96 1.98 2.00

Frequency (GHz)

S11, S22 (dB)

S11 S22

ACLR vs. Output Average Power vs. Frequ ency

T=25°C

-60

-55

-50

-45

-40

10 12 14 16 18

Output Power (dBm)

ACLR (dBc)

1930 MHz 1960 MHz 1990 MHz

OIP3 vs . Output Power/Tone vs. Frequency

T=25°C

5 7 9 11 13 15

Output Power/Tone (dBm)

OIP3 (dBm)

1930 MHz 1960 MHz 1990 MHz

Current vs Output Average Power vs. Frequency

T=25°C

100

120

140

160

180

200

12 14 16 18 20 22 24

Output Power (dBm)

Collector Current (mA)

1930 MHz 1960 MHz 1990 MHz

NF vs. Frequency

T=25°C

1.90 1.92 1.94 1.96 1.98 2.00

Frequency (GHz)

NF (dB)

Specifications and information are subject to change without notice

TriQuint Semiconductor Inc • Phone 1-503-615-9000 • FAX: 503-615-8900 • e-mail: info-s ales@tqs.com • Web site: www.TriQuint.com Page 6 of 8 Aug 2009

AH128

¼W Hi

h Linearit

InGaP HBT Am

lifier

2110-2170 MHz Reference Design (AH128-89PCB2140)

W-CDMA 3GPP Test Model 1+64 DPCH, PAR = 9.7 dB @ 0.01% Probability, 3.84 MHz BW

Typical W-CDMA Performance at 25°C

Frequency (MHz) 2110 2140 2170 Units

Gain 16.6 16.6 16.7 dB

Input Return Loss 12 13 13 dB

Output Return Loss 11 10 10 dB

ACLR

Pout=+15 dBm -49 -51 -52 dBc

Output P1dB +24.6 +24.6 +24.6 dBm

Output IP3

Pout=10dBm/tone, 1MHz spacing +42.3 +41.5 +41.8 dBm

Noise Figure 4.4 4.4 4.5 dB

Quiescent Current, Icq 115 mA

Vcc +5 V

Notes:

1. The primary RF microstrip line is 50 Ω.

2. Components shown on the silkscreen but not on the schematic are not used.

3. 0 Ω jumpers can be replaced with copper trace in target application.

4. The edge of C9 is placed at 250mil from AH128 RFout pin. (29.6 o @ 2140 MHz)

5. The edge of R1 is placed at 100mil from AH128 RFin pin. (12 o @ 2140 MHz)

6. The edge of C10 is placed 180mil from the edge of R1. (21.3 o @ 2140 MHz)

Gain vs. F requency

T=25°C

2.10 2.12 2.14 2.16 2.18 2.20

Frequency ( GHz)

Gain (dB)

Return Loss

T=25°C

-25

-20

-15

-10

-5

2.10 2.12 2.14 2.16 2.18 2.20

Frequency (GHz)

S11,S22 (dB)

S11 S22

OIP3 vs. Output Power/Tone vs. Temperature

f=2140 MHz

6 8 10 12 14 16

Output Power/Tone (dBm)

OIP3 (dBm)

+25°C -40°C +85°C

ACLR vs. Output Average Power vs. Frequ ency

T=25°C

-65

-60

-55

-50

-45

-40

8 10121416

Output Power (dBm)

ACLR (dBc)

2110 MHz 2140 MHz 2170 MHz

ACLR vs. Output Average Power vs. Temperature

f=2140 MHz

-65

-60

-55

-50

-45

-40

8 10121416

Output Power (dBm)

ACLR (dBc)

+25°C -40°C +85°C

OIP3 vs . Output Power/Tone vs. Frequency

T=25°C

6 8 10 12 14 16

Output Power/Tone (dBm)

OIP3 (dBm)

2110 MHz 2140 MHz 2170 MHz

NF vs. Frequency

T=25°C

2.10 2.12 2.14 2.16 2.18

Frequency (GHz)

NF (dB)

Current vs Output Average Power vs. Frequency

T=25°C

100

120

140

160

180

200

12 14 16 18 20 22 24

Output Power (dBm)

Collector Current (mA)

2110 MHz 2140 MHz 2170 MHz

Specifications and information are subject to change without notice

TriQuint Semiconductor Inc • Phone 1-503-615-9000 • FAX: 503-615-8900 • e-mail: info-s ales@tqs.com • Web site: www.TriQuint.com Page 7 of 8 Aug 2009

AH128

¼W Hi

h Linearit

InGaP HBT Am

lifier

2.5-2.7 GHz Application Circuit Performance Plots

802.16-2004 O-FDMA, 64QA M-1/2, 1024-FFT, 20 sy mbols and 30 subchannels, 5 MH z Carrier B W

Typical O-FDMA Performance at 25°C

Frequency (GHz) 2.5 2.6 2.7 Units

Gain 14.7 15.1 14.9 dB

Input Return Loss 7.1 13 13 dB

Output Return Loss 15 10 8.1 dB

EVM

Pout=+17 dBm 2.4 2.4 2.3 %

Output P1dB 24.5 24.8 24.7 dBm

Output IP3

Pout=+8 dBm/tone, 1MHz spacing 41.1 40.8 41.5 dBm

Quiescent Current, Icq 115 mA

Vcc +5

C2R2

C10

Notes:

1. The primary RF microstrip line is 50 Ω.

2. Components shown on the silkscreen but not on the schematic are not used.

3. 0 Ω jumpers can be replaced with copper trace in target application.

4. The edge of C9 is placed at 230 mil from AH128 RFout pin. (32o @ 2.5 GHz)

5. The edge of R1 is placed at 100 mil from AH128 RFin pin. (14o @ 2.5 GHz)

6. The edge of C10 is placed 25 mil from the edge of R1. (3.5o @ 2.5 GHz)

Gain vs. Frequency

T=25°C

2.40 2.50 2.60 2.70 2.80

Frequency (GHz)

Gain (dB)

Return Loss

T=25°C

-30

-25

-20

-15

-10

-5

2.40 2.50 2.60 2.70 2.80

Frequency (GHz)

S11, S22 (dB)

S11 S22

EVM vs. Output Average Power vs. Frequency

T=25°C

8 1012141618

Output Power (dBm)

EVM (%)

2.5 GHz 2.6 GHz 2.7 GHz

ACLR vs. Output Average Power vs. Frequency

T=25°C

-60

-55

-50

-45

-40

-35

8 1012141618

Output Power (dBm)

ACLR (dBc)

2.5 GHz 2.6 GHz 2.7 GHz

W-CDMA 3GPP Test Mo del 1+64 DPCH

PAR = 10.2 dB @ 0.01% Probabili ty

3.84 MHz BW

OIP3 vs. Output Power/Tone vs. Frequency

T=25°C

6 8 10 12 14 16 18 20

Output Power/Tone (dBm)

OIP3 (dBm)

2.5 GHz 2.6 GHz 2.7 GHz

Specifications and information are subject to change without notice

TriQuint Semiconductor Inc • Phone 1-503-615-9000 • FAX: 503-615-8900 • e-mail: info-s ales@tqs.com • Web site: www.TriQuint.com Page 8 of 8 Aug 2009

AH128

¼W Hi

h Linearit

InGaP HBT Am

lifier

Mechanical Information

This package is lead-free/Green/RoHS-compliant. It is compatible with both lead-free (maximum 260 °C reflow temperature) and leaded

(maximum 245 °C reflow temperature) soldering processes. The plating material on the leads is NiPdAu.

Outline Drawing

Land Pattern

Product Marking

The AH128 will be marked with an

“AH128G” designator with a lot code marked

below the part designator. The “Y” represents

the last digit of the year the part was

manufactured, the “XXX” is an auto-

generated number, and “Z” refers to a wafer

number in a lot batch.

Tape and reel specifications for this part are

located on the website in the “Application

Notes” section.

MSL / ESD Rating

ESD Rating: Class 2

Value: Passes 2000V to <4000V

Test: Human Body Model (HBM)

Standard: JEDEC Standard JESD22-A114

ESD Rating: Class IV

Value: Passes ≥ 2000V min.

Test: Charged Device Model (CDM)

Standard: JEDEC Standard JESD22-C101

MSL Rating: Level 3 at +260 °C convection reflow

Standard: JEDEC Standard J-STD-020

Mounting Config. Notes

1. Ground / thermal vias are critical for the proper performance of

this device. Vias should use a .35mm (#80 / .0135”) diameter

drill and have a final plated thru diameter of .25 mm (.010”).

2. Add as much copper as possible to inner and outer layers near

the part to ensure optimal thermal performance.

3. Mounting screws can be added near the part to fasten the board

to a heatsink. Ensure that the ground / thermal via region

contacts the heatsink.

4. Do not put solder mask on the backside of the PC board in the

region where the board contacts the heatsink.

5. RF trace width depends upon the PC board material and

construction.

6. Use 1 oz. Copper minimum.

7. All dimensions are in millimeters (inches). Angles are in

degrees.

YXXX-Z

AH128G