4-507

Product Description

Ordering Information

Typical Applications

Features

Functional Block Diagram

RF Micro Devices, Inc.
7628 Thorndike Road
Greensboro, NC 27409, USA

Tel (336) 664 1233

Fax (336) 664 0454

http://www.rfmd.com

Optimum Technology Matching® Applied

Si BJT

GaAs MESFET

GaAs HBT

Si Bi-CMOS

SiGe HBT

Si CMOS

InGaP/HBT

GaN HEMT

SiGe Bi-CMOS

RF OUT

VCC

GND

RF IN

RF2472

2.4GHz LOW NOISE AMPLIFIER WITH ENABLE

· TDMA/CDMA PCS LNA
· TDMA/CDMA/FM Cellular LNA
· ISM Band LNA/Driver

· Low Noise Transmit Driver Amplifier
· General Purpose Amplification
· Commercial and Consumer Systems

The RF2472 is a general purpose, low-cost, high-perfor-
mance amplifier designed for operation from a 2.7V to 4V
supply with low current consumption. The device is opti-
mized for 2.4GHz LNA applications, but is also useful for
1.9GHz PCS and K-PCS, 900MHz ISM, and 1.5GHz
GPS applications. The RF2472 is available in a very
small industry-standard SOT23 5-lead surface mount
package, enabling compact designs which conserve
board space.

· DC to >6GHz Operation
· 2.7V to 4.0V Single Supply
· High Input IP

· 1.5dB Noise Figure at 2400MHz
· 14dB Gain at 2400MHz
· Low Current Consumption of 6mA at 3V

RF2472

2.4GHz Low Noise Amplifier with Enable

RF2472 PCBA-410Fully Assembled Evaluation Board, 2.4GHz
RF2472 PCBA-411Fully Assembled Evaluation Board, 1.9GHz

Rev A8 030124

1.60

+ 0.01

0.400

2.80

+ 0.20

2.90

+ 0.10

0.45

+ 0.10

3° MAX

0° MIN

0.127

0.15
0.05

1.44
1.04

Dimensions in mm.

0.950

Package Style: SOT 5 Lead

Preliminary

Preliminary

4-508

RF2472

Rev A8 030124

Absolute Maximum Ratings

Parameter

Rating

Unit

Supply Voltage

-0.5 to 4.0

Input RF Level

dBm

Operating Ambient Temperature

-40 to +85

°C

Storage Temperature

-40 to +150

°C

Parameter

Specification

Unit

Condition

Min.

Typ.

Max.

Overall

T=27°C, V

=3.0V

Frequency Range

DC to >6000

MHz

2.4GHz LNA Operation

T=27°C, V

=3.0V, Freq=2440MHz

Gain

13.0

14.6

17.0

Noise Figure

1.5

Input IP3

+8.0

+10.0

+20.0

dBm

Two tones at 1MHz spacing, -15dBm output

Input P

1dB

-10

dBm

PCS and K-PCS LNA
Operation

T=27°C, V

=3.0V, Freq=1960MHz

Gain

16.3

Noise Figure

1.4

Input IP3

dBm

Two tones at 1MHz spacing, -12dBm output

Input P

1dB

-12

dBm

Power Supply

Operating Voltage

2.7 to 3.6

Operating Current

4.0

6.0

8.0

=3.0V, PD=3.0V

<1.0

3.0

=3.0V, PD=0V

Caution! ESD sensitive device.

RF Micro Devices believes the furnished information is correct and accurate
at the time of this printing. However, RF Micro Devices reserves the right to
make changes to its products without notice. RF Micro Devices does not
assume responsibility for the use of the described product(s).

Preliminary

4-509

RF2472

Rev A8 030124

Pin

Function

Description

Interface Schematic

VCC

Supply connection. An external bypass capacitor may be required in

some applications.

See pin 3.

GND

Ground connection. Keep traces physically short and connect immedi-

ately to ground plane for best performance.

RF IN

RF input pin. This pin is DC coupled and matched to 50

at 2.4GHz.

Power down pin.This pin enables the bias to the amplifier. To turn the

amplifier on, this pin should be connected to V

. Connecting this pin

to ground, will turn the amplifier off and reduce the current draw to

below 1

A. This pin is a CMOS input. There is no DC current draw

other than the transient current required to charge or discharge the

gate capacitance (less than 5pF).

RF OUT

LNA Output pin.This pin is an open-collector output. It must be biased

to V

through a choke or matching inductor. This pin is typically

matched to 50

with a shunt bias/matching inductor and series block-

ing/matching capacitor. Refer to application schematics.

See pin 3.

RF IN

RF OUT

VCC

BIAS

Preliminary

4-510

RF2472

Rev A8 030124

Theory of Operation

The RF2472 is a low-noise amplifier with internal bias
circuitry. It is DC-coupled on the input and output;
therefore, it can be used to arbitrarily low frequency. It
has useful gain to above 6GHz. Its design is optimized
for use at 2.4GHz. Because of the high-frequency
gain, the designer must take care to ensure that the
device will remain stable outside the desired operating
frequency. The RF2472 is capable of providing out-
standing linearity, but to achieve this high performance,
the circuit designer must pay attention to the termina-
tions that are presented to low-frequency intermodula-
tion products.

Stability
The RF2472 must be stabilized for frequencies outside
of the desired operating range. Ground connections
should be kept as short as possible. Wherever practi-
cal, ground should be provided by a via hole directly to
a continuous ground layer. Highly reflective termina-
tions to the RF input and output pins should be avoided
whenever possible. In most circumstances, a resistor
in parallel with an inductor in the bias line on pin 5 will
improve the stability of the circuit. See the application
schematics for examples. The 10nH inductor in the
bias line is part of an output impedance matching cir-
cuit. At higher frequencies, the impedance of the
matching circuit, alone, would become highly inductive.
The large reactive termination of the output port could
cause the circuit to oscillate at a high frequency. The
resistance in parallel with the inductor adds a real part
to the high-frequency termination that will have a stabi-
lizing effect on the circuit.

Linearity
The 22nF bypass and coupling capacitors in the appli-
cation schematics may seem excessively large for cir-
cuits intended to operate at 1.9GHz and 2.4GHz.
These large capacitors provide a low impedance path
to ground for second-order mixing products that leads
to improved third-order intermodulation performance.
The effect is most easily seen for the input coupling
capacitor. A 100pF capacitor would provide low
enough impedance to couple a 2.4GHz signal into the
input pin of the RF2472. However, low-frequency inter-
modulation products caused by second-order nonlin-
earities would be presented with a large reactive
impedance at the input pin. Relatively large voltages
for these low-frequency products would be allowed to
mix with the fundamental signals at the input pin,
resulting in relatively large, in-band, third-order prod-
ucts.

With a large coupling capacitor, the low-frequency
products would be presented with a low impedance,
via the input source impedance, resulting in a lower
voltage at the input pin. These products, in turn, would
mix at a lower level with the fundamental signals to
produce lower in-band, third-order products.

Some designers may be concerned about the self-res-
onant frequency of large coupling capacitors. A 22nF
capacitor will probably pass through self resonance
below 100MHz. Beyond resonance, the reactance of
the capacitor will turn inductive, but the internal losses
of the capacitor will usually prevent the component
from exhibiting a large reactive impedance.

Third-Order Intercept versus 1-dB Compression
Point
For many devices, the third-order intercept point is
approximately 10dB higher than the 1-dB compression
point. This rule of thumb does not apply for the
RF2472. It is normal to find that the third-order inter-
cept point is 20 dB higher than the 1-dB compression
point. This behavior is common for SiGe devices. The
reason for the difference is that the 10dB rule is based
on a simple third-order polynomial model for device
nonlinearities. For SiGe devices this simple model is
not a good fit.

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