The ADA4939-1 / ADA4939-2 are low noise, ultralow distortion, high speed differential amplifiers. They are an ideal choice for driving high performance ADCs with resolutions up to 16 bits from dc to 100 MHz. The output common-mode voltage is user adjustable by means of an internal common-mode feedback loop, allowing the ADA4939-1 / ADA4939-2 output to match the input of the ADC. The internal feedback loop also provides exceptional output balance as well as suppression of even-order harmonic distortion products.
With the ADA4939-1 / ADA4939-2, differential gain configurations are easily realized with a simple external feedback network of four resistors that determine the closed-loop gain of the amplifier.
The ADA4939-1 / ADA4939-2 are fabricated using Analog Devices, Inc., proprietary silicon-germanium (SiGe), complementary bipolar process, enabling them to achieve very low levels of distortion with an input voltage noise of only 2.3 nV/√Hz. The low dc offset and excellent dynamic performance of the ADA4939-1 / ADA4939-2 make them well suited for a wide variety of data acquisition and signal processing applications.
The ADA4939-1 (single) is available in a 3 mm × 3 mm, 16-lead LFCSP, and the ADA4939-2 (dual) is available in a 4 mm × 4 mm, 24-lead LFCSP. The pinouts are optimized to facilitate printed circuit board (PCB) layout and minimize distortion. The ADA4939-1/ADA4939-2 are specified to operate over the −40°C to +105°C temperature range; both operate on supplies between 3.3 V and 5 V.
Applications
ADC drivers
Single-ended-to-differential converters
IF and baseband gain blocks
Differential buffers
Line drivers
### Features and Benefits
Extremely low harmonic distortion
−102 dBc HD2 at 10 MHz
−83 dBc HD2 at 70 MHz
−77 dBc HD2 at 100 MHz
−101 dBc HD3 at 10 MHz
−97 dBc HD3 at 70 MHz
−91 dBc HD3 at 100 MHz
Low input voltage noise: 2.3 nV/√Hz
High speed
−3 dB bandwidth of 1.4 GHz, G = 2
Slew rate: 6800 V/μs, 25% to 75%
Fast overdrive recovery of <1 ns
±0.5 mV typical offset voltage
Externally adjustable gain
Stable for differential gains ≥2
Differential-to-differential or single-ended-to-differential operation
