Amplifiers’ performance/power scales to tasks
01 November 2007
Three amplifiers have been launched by National Semiconductor (www.nsc.com) and illustrate the company’s extension of the PowerWise, energy-efficiency initiative.
The first amplifier, the LMH6552, has a fast settling time and can be used in time-domain devices, such as oscilloscopes. The LMH6552, current feedback differential amplifier, boasts the industry’s highest bandwidth, 1.5GHz, and a low power consumption of 112mW. This is equivalent to 44 per cent less power than competitive products, claims the company. It is a digital-controller, variable gain amplifier with an 8dB noise figure and a 40dBm output intercept point at 70MHz for WCDMA, GSM and WiMAX receiver signal paths at 20 per cent less power than competitive alternatives.
The LMH6515 is a digital-controlled variable gain amplifier, for high-frequency applications, such as basestations and military radio. It maximises dynamic range of the signal path in IF sampling applications and has the same high linearity as the 6552. Coupled with low noise, it can be used for broadband and narrowband receiver paths. It consumes just 100mA and operates at 5V supply and is packaged in a 4mm x 4mm, 16pin LPP. This is claimed to reduce board space by more than 75 per cent compared to a discrete attenuator and amplifier solution. In receiver applications, maximum gain is 26dB and gain adjustment is
31dB with 600MHz bandwidth.
The LM6555 differential driver is claimed to be the only one optimised for DC-coupled, 8bit data acquisition applications, with input frequencies up to 750MHz. SFDR performance is 53dB at 750MHz, described as industryleading by National. There is no need to add external circuitry for output clamping, commonmode
control and gain. The driver converts single-ended signals into differential ones, while providing a fixed gain of 13.7dB and a 1.2GHz bandwidth.
Reference boards are also available. The ADC14DS105KARB low IF receiver design board, uses two LMH6552 differential drivers and a dual ADC to evaluate quadrature direct conversion or near-zero IF receiver for signal frequencies from DC to 40MHz, an architecture commonly used in WiMAX and WCDMA
receiver systems. The ADC14V155KDRB uses an LMH6515 and ADC to evaluate dynamic range IF sampling. The ADC083000RB is an 8bit, 3Gsample/sec data acquisition board, using an LMH6555 and ADC to evaluate parts for test and measurement equipment or for high-speed communication systems in space and defence systems.
The PowerWise initiative was launched four years ago, when the company worked with ARM to produce devices that assess and scale voltages to adapt to what is happening. Now, the PowerWise brand also applies to selected high performance products and sub-systems so that customers can gauge the optimum power performance upon assembly.
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