ADA4961 Datasheet, PDF (1/25 Pages) Analog Devices – Digitally adjustable gain

Data Sheet
Low Distortion, 3.2 GHz, RF DGA
ADA4961
FEATURES
High speed
−3 dB bandwidth: 3.2 GHz
−1 dB bandwidth: 1.8 GHz
Slew rate: 12,000 V/μs
Digitally adjustable gain
Voltage gain: −6 dB to +15 dB
Power gain: −3 dB to +18 dB
5-bit parallel or SPI bus gain control with fast attack
IMD3/HD3 distortion, maximum gain, 5 V, high performance
(HP) mode
IMD3/HD3 at 1 GHz: −90 dBc/−83 dBc
IMD3/HD3 at 1.5 GHz: −85 dBc/−75 dBc
IMD3/HD3 at 2 GHz: −70 dBc/−70 dBc
Low noise
Noise density referred to output (RTO): −154 dBm/Hz
Noise figure: 5.5 dB at AV = 15 dB, 1 GHz
Differential impedances: 100 Ω input, 50 Ω output
Low power mode operation, power-down control
Single 3.3 V or 5 V supply operation
Available in 24-lead, 4 mm × 4 mm LFSCP
APPLICATIONS
ADC driver for 10-bit to 14-bit GSPS converters
RF/IF gain blocks
Line drivers
Instrumentation
Satellite communications
Data acquisition
Military systems
GENERAL DESCRIPTION
The ADA4961 is a high performance, BiCMOS RF digital gain
amplifier (DGA), optimized for driving heavy loads out to
2.0 GHz and beyond. The device typically achieves −90 dBc
IMD3 performance at 500 MHz and −85 dBc at 1.5 GHz. This
RF performance allows GHz converters to achieve their optimum
performance with minimal limitations of the driver amplifier or
constraints on overall power that typically result from GaAs
amplifiers. This device can easily drive 10-bit to16-bit HS
converters.
For many receiver applications, antialias filter (AAF) designs
can be simplified or not required.
The ADA4961 has an internal differential input impedance of
100 Ω and a differential dynamic output impedance of 50 Ω,
eliminating the need for external termination resistors. The
FUNCTIONAL BLOCK DIAGRAM
24 23 22 21
20 19
EXPOSED
PAD
ADA4961
VIN+ 2
0dB TO 21dB
ATTEN
+15dB
17 VOUT+
VIN– 3
16 VOUT–
GND 4
18 DNC
15 DNC
GND 5
14 _DNC
1 7 8 9 10 11 12 13 6
NOTES
1. DNC = DO NOT CONNECT. DO NOT CONNECT TO THIS PIN.
Figure 1.
digital adjustability provides for 1 dB resolution, thus optimizing
the signal-to-noise ratio (SNR) for input levels spanning 21 dB.
The ADA4961 is optimized for wideband, low distortion
performance at frequencies up to 2 GHz. These attributes,
together with wide gain adjustment and relatively low power,
make the ADA4961 the amplifier of choice for many high speed
applications, including IF, RF, and broadband applications
where dynamic range at very high frequencies is critical.
The ADA4961 is ideally suited for driving not only analog-to-
digital converters (ADCs), but also mixers, pin diode
attenuators, SAW filters, and multielement discrete devices. It is
available in a 4 mm × 4 mm, 24-lead LFCSP and operates over a
temperature range of −40°C to +85°C.
Rev. A
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