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REVIEW: RFIC families to ease microwave circuit design

ANALOG DEVICES OFFERS INDUSTRY'S MOST COMPLETE RF PORTFOLIO WITH ADDITION OF RF/IF AMPLIFIERS

Four new RF amplifier families deliver industry's best performance for the entire RF signal chain

NORWOOD, Mass.—Analog Devices, Inc., a global leader in high-performance semiconductors for signal processing applications, expands its industry-leading RF (radio frequency) solutions with the introduction today of an RF amplifier portfolio of 12 new devices covering the complete RF signal chain. Combined with ADI's industry-leading power detectors, modulators, demodulators, mixers, and synthesizer products, this offering allows designers to implement complete signal chain solutions using Analog Devices' high-performance ICs, thereby simplifying the design process, streamlining supply chain logistics, and shortening time to market.

The new RF amplifiers are fully characterized and specified for both broad-band and narrow-band applications. When coupled with ADI's other RFICs, they enable the design and implementation of advanced RF radio architectures for a wide range of performance-driven applications, such as communications infrastructure equipment, marine radar and RFID readers.

With unprecedented levels of performance, the four RF amplifier product families include, LNAs (low-noise amplifiers), IFAs (intermediate frequency amplifiers), driver amplifiers, and RF gain blocks, all of which are fully specified for operation over temperature, supply voltage and operating frequency, thereby easing the selection and design-in process.

Within each RF amplifier family, Analog Devices optimized the performance to cover both broadband and narrowband applications with the minimum number of external passive components, providing considerable savings in board area and design complexity.

“The RF amplifiers support the higher performance and wider bandwidth applications within next-generation broadband access systems, without sacrificing cost, size or power consumption. Each RF amplifier family provides leading linearity performance, minimizes external component count, and is fully specified and characterized to simplify the design-in process,” said Peter Real, product line director for RF and Networking Components, Analog Devices. “Analog Devices is providing the highest performance RF ICs that enable designers creative freedom to implement new cost efficient radio architectures across the many markets and air interface standards.”

LOW NOISE AMPLIFIERS (LNAs): As the first amplifier in the receive path, LNAs are a critical component for defining overall system performance and must be able to successfully amplify very low-level signals without adding a significant amount of noise. ADI's ADL552x family sets an industry performance benchmark by operating from 400 MHz to 4 GHz while achieving a low noise figure with the optimum amount of gain and current consumption. The ADL5521 provides 0.8 dB NF with a gain of 15 dB while the ADL5523 provides 1.1dB NF with a gain 17.5 dB. The new LNA family includes on-chip bias circuitry and requires minimal external matching components, thereby reducing cost and board space compared to discrete low-noise amplifiers. For more information, visit www.analog.com/rfamps.

INTERMEDIATE FREQUENCY AMPLIFIERS (IFAs): Designed to operate in the IF frequency range typically below 500 MHz, ADI's ADL553x family of single- and dual-channel IFAs are fully specified and characterized to support applications across the most commonly used IF frequencies of 70, 140, 190, 240, and 380 MHz. The new IFAs provide industry's highest linearity of 41 dBm while maintaining a noise figure as low as 2.5 dB for optimal signal dynamic range. Compared to competing products, the new IFA family provides the highest linearity specifications and is offered within space saving surface mount LFCSP packages. Furthermore, Analog Devices' IFAs integrate on-chip bias circuitry, require minimal external matching components and support 1KV Class 1C ESD. For more information, visit www.analog.com/rfamps.

DRIVER AMPLIFIERS: Analog Devices' ADL532x driver amplifier family offers the highest linearity for a given output power to enable low distortion, high-output drive directly to the power amplifier stages. The ADL5320 driver provides broadband operation from 400 MHz to 2.7 GHz and requires minimal external matching for a chosen band of operation. The ADL5320 provides an output linearity of 42 dBm and 26 dBm output compression point while consuming just 104 mA of supply current. The ADL5322 and ADL5323 drivers are optimized to work over frequency bands of 700 MHz to 1 GHz and 1.7 GHz to 2.4 GHz, respectively and provide the highest linearity with an output IP3 of 45dBm and output compression point of 28dBm. The ADL5322 and ADL5323 are internally matched and can eliminate the need for up to 10 external components required. Both devices provide exceptional adjacent channel power ratio for CDMA and W-CDMA applications. For example the ADL5323 provides better than 70dBc ACPR while delivering greater than +10dBm output power. Compared to competing devices, Analog Devices' driver amplifiers integrate on-chip bias circuitry, minimize the need for external matching components, and support the highest linear output drive levels for the transmitter output power stages. For more information, visit www.analog.com/rfamps.

Gain Blocks: The ADL5541 and ADL5542 are broadband gain blocks that operate from low frequencies up to 6 GHz. Both devices are 50-ohm internally matched with integrated internal bias circuitry minimizing the need for external components. The ADL5541 provides 15 dB gain with output linearity of 40dBm and the ADL5542 provides 20 dB of gain with an output linearity of 40dBm. Both devices are fully ESD protected and available in small footprint LFCSP packages. Compared to competing devices, the ADL5541 and ADL5542 offer the highest linearity and lowest noise figures across a broader operating frequency range, while saving board area and cost due to the smaller footprint surface mount packaging. For more information, visit www.analog.com/rfamps.

Pricing and Availability


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ADI in Radio Frequency ICs

Using a unique combination of design skills, process technologies, and system understanding, Analog Devices offers a broad portfolio of RF ICs, including complete chipsets and a full range of high-performance RF function blocks. ADI's extensive offerings include: direct digital synthesizers (DDS); phase-locked loop synthesizers (PLLs); detectors and logarithmic amplifiers; X-AMP fixed and variable gain amplifiers (VGAs); TruPwr RF power detectors; mixers, modulators, and demodulators; integrated IF amplifiers; and the Othello family of single-chip transceivers for cellular terminals. For more information, visit www.analog.com/rfamps.

This panoply of lead-frame CSP (chip-scale-packaged) RF amplifier chips (with one exception) from Analog Devices Inc . (ADI) is impressive. These tiny surface-mount devices give you a straightforward and repeatable way to implement critical RF signal amplification and processing blocks.

Although they're still being characterized, and datasheets are preliminary, ADI's $2.15 ADL5521 and ADL5523 LNA s (low-noise amplifiers) tout noteworthy NF (noise-figure) specs. The ADL5521 exhibits a 0.8-dB NF (at 1.9-GHz). The ADL5523 LNA's NF comes in at just 1.1-dB.

That's significant, as the NF of an LNA is an indicator of the contribution by the LNA itself to thermal noise at its output. NF, expressed in dB, is a value with respect to thermal noise power (at the system impedance, at a standard noise temperature [usually 20°C or 293°K] over the bandwidth of interest).

NF is determined by measuring the ratio in dB, of the thermal noise power at the output, to that at the input, and subtracting from that result, the gain, in dB, of the system.

Low Real Estate

In addition to the very low NF specs, ADI's LNAs should be relatively straightforward to implement. Thanks to on-chip bias circuitry and the need for very few matching components, these parts should fill the bill in simplified designs that occupy low circuit-board real estate.

Not mentioned in ADI's press statement is that its LNAs are GaAs (gallium arsenide) pHEMT (pseudomorphic high electron-mobility transistor) devices. The 5-V ADL5521 can be used from 400-MHz to 4-GHz, with 50-ohm AC-coupled I/Os. Typical gain is better than 15-dB.

The ADL5521's third-order intercept point (IP3) is 35.3-dB (at 1.9-GHz). With external matching, input return loss is typically 12-dB, with output return loss at 20.7-dB. Similarly, the ADL5523, offering a gain of 17.5-dB, has an output IP3 spec of 33.7-dB. Both packages employ exposed pads (or paddles) to ensure a low-Z path to ground planes.

IF-Strip Devices

Okay, the front-end of your system is covered. Let's look at the IF strip. ADI is offering five devices for IF applications. The ADL5530, ADL5531 , and ADL5534 are sampling now; the ADL5532 and ADL5533 chips are expected by mid-summer.

The $1.56 ADL5530 is a broadband single-ended gain-block that can be used from DC out to 1-GHz. Operable from 3-V to 5-V, it offers a gain spec of 16.5-dB, and a good NF of 3-dB. It also uses internal matching to ensure a good match to 50-ohm lines, and shows an input return loss of 11- dB. In use, all you need add is a few I/O coupling capacitors, a power supply de-coupling cap, and an external inductor.

Like the front-end devices, the ADL5530 is a GaAs pHEMT chip, as is the ADL5531. Not as broad-banded as the ADL5530, ADI's $2.25 ADL5531 gain block can operate from 20-MHz to 500-MHz.

Two Amplifiers In One Package

Similarly, the $3.29 ADL5534 is essentially a dual-section ADL5531. Good up to 500-MHz, it packs two broadband fixed-gain linear amplifiers in a single package that draws about 90-mA/amplifier from a 5-V source. It's NF is 2.5-dB (at 70-MHz).

The ADL5532 and ADL5533, slated for release in July, comprise additional broadband linear amplifiers operable to 500-MHz. To be priced at about $2.25 a pop, the single-ended ADL5532 is gain-stable over frequency, temperature, and power supply variations, as well as from device to device. It gives you a third-order intercept spec of 39.1-dBm, with an output compression point of +19.9-dBm, and a NF of 3-dB.

Like the other devices, the pHEMT ADL5532 is internally matched to 50-ohms. It exhibits an input return loss of 10-dB. For its part, the $2.55 ADL5533 fixed-gain amplifier will operate to 1-GHz. Gain is 20-dB, IP3 is +37.3-dBm, and output compression point is +18.8-dBm. NF is specified as 2.9-dB.

SOT-39 Packaging

Departing from the lead-frame CSP packaging of the other devices in this product roll-out, ADI's ADL5320 broadband linear amplifier is slated as a pre-driver device. Packaged as a SOT-39 device, the $2.55 is available in sampling. The ADL5320 is intended for applications from 400-MHz through to 2.7-GHz, where it gives a gain of 13.7-dB (at 2.14-GHz). Its IP3 is +42-dBm (also characterized at 2.14-GHz). The 5-V ADL5320 sports a NF spec of 4.2-dB.

Also now in sampling, ADI's CSP-packaged ADL5322 is billed as a driver amp. It's for operation over the 700-MHz to 1-Ghz range. This amplifier, with a gain spec of 20-dB, is slated for use in the output stage of a cellular base station radio, or as an input preamp in a multi-carrier base station PA (power amplifier). Matching and biasing are all on-chip.

The ADL5323 , priced at $3.48, is also a driver amplifier, but it's for use from 1.7-GHz to 2.4-GHz. Like the ADL5322, the ADL5323 has a gain of 20 dB, and impedance matching and biasing are on-chip.

Operation Out To 6-GHz

The final two devices in ADI's offering series are broadband 5-V-only 15-dB and 20-dB linear amplifiers that can operate at frequencies up to 6-GHz. Dubbed “gain blocks,” ADI's ADL5541 and ADL5542 , priced at $1.65 each, are fabricated on an InGaP (indium-gallium-phosphide) high-voltage HBT (heterojunction bipolar transistor) process, needed to reach this microwave regime.

The ADL5541, with its 15-dB gain spec, is stable over frequency, temperature, and power supply variations, and from device to device. It achieves IP3 of 40.9-dBm, with an output compression point of 18.2-dBm, and an impressive NF spec of 3.5-dB (at 900 MHz).

The 20-dB gain ADL5542 achieves an IP3 of 40-dBm, with an output compression point of 20.6-dBm, and a NF of 3-dB (at 900 MHz). Both amplifiers are internally matched to 50-ohms, and show input return loss specs of 10-dB or better up to 6-GHz. Only input/output ac-coupling capacitors, power supply decoupling caps, and an external inductor are required for operation.

Evaluation Boards


Click to view eval board schematic

ADI also has populated eval boards available for these above mentioned devices. The evaluation platforms should go a long way to ease the pain of developing stable circuits at microwave frequencies.

For more information, contact Analog Devices, Inc., 804 Woburn St., Wilmington, Mass. 01887. Phone: 800-ANALOGD (800-262-5643) or 781-937-1428. Fax: 781-937-1021.

Analog Devices , 800-262-5643, www.analog.com

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