HBT Devices Deliver Gain/Linearity To 2.4 GHz

This family of discrete devices provides up to 4 W over moderate bandwidths with the linearity essential to wireless base-station amplifiers.

Linearity has become a driving requirement for wireless amplification, especially with the push toward more efficient bandwidth usage and more complex modulation formats. Discrete devices, such as the MMA709 heterojunction-bipolar transistor (HBT) from Aeroflex/Metelics (Sunnyvale, CA) provide the clean performance sought by amplifier designers, while also offering the flexibility of a discrete transistor. The HBT can achieve output levels to +33 dBm (2 W) over moderate bandwidths within the 100-to-2400-MHz range.

The MMA709 (see figure) is a member of the company's growing line of indium-gallium-phosphide (InGaP) HBT-based discrete devices and monolithic microwave integrated circuits (MMICs) for commercial and military amplifier applications. These semiconductors compare favorably with other device technologies such as GaAs and silicon LDMOS in terms of cost while offering significant advantages in linearity.

At present, model MMA709 is one of four devices available for applications through 2.4 GHz with varying performance levels. The devices are supplied in low-profile QFN-style 3 × 3-mm and 6 × 6-mm packages as well as industry-standard SOT-89 and SOIC8 housings. (The MMA709 is supplied in 3 × 3-mm QFN and SOIC8 packages.) Key specifications for all four devices are shown in the table. The MMA709 is characterized for Class A operation and is available in the "3030" and SOIC8 packages.

The MMA709 typically delivers 11 dB gain in the 1930-to-1990-MHz PCS band with +34 dBm associated output power and +54 dBm third-order intercept point when operating on 700 mA and +7 VDC. The third-order-intercept performance remains flat with frequency over the PCS band. The noise figure is 6.5 dB. The thermal resistance, as measured with an infrared (IR) microscope, is less than 12°C/W.

In addition to the MMA709 discrete device, the company also launched its MMA712 gain block, with input and output ports matched to 50 (omega) and resulting 3-dB bandwidth of 17 GHz. The gain block features typical gain of 12 dB from 1 to 18 GHz with output power at 1-dB compression of +11 dBm and input third-order intercept of +23 dBm. The noise figure is typically 5.5 dB. The gain block draws 48 mA nominal current from a minimum supply of +6 VDC.

To address the need for high-reliability (Hi-Rel) vesions of these transistors and gain blocks, the firm has developed a program to cover screening per military (MIL) standards. The process features include eutectic die attach, gold wire bonding and hermetic, thermally enhanced packages. Devices are characterized over extended bandwidths and temperature ranges with maximum ratings that conform to JEDEC/IEC standards.

For example, JANTXV and JANS equivalent screening of package discrete devices is available in accordance with MIL-PRF-19500 and Class B and Class S equivalent screening is available for packaged MMICs in accordance with MIL-PRF-38535. Die are available with Class K and H die element evaluation in accordance with MIL-PRF-8534. The company also has a cost-effective screening program called COTS Plus for plastic encapsulated parts that incorporates all core screens and is applicable to the company's MMIC products. It includes 100-percent temperature cycling, thermal shock, burn-in at the maximum junction temperature, and full DC/RF testing. P&A: MMA709-30 (3030 pkg.) $11.22, 100 qty; MMA709-S8 (SOIC8 pkg.) $10.09, 100 qty. Both versions are available from stock. Aeroflex/Metelics, 975 Stewart Dr., Sunnyvale, CA 94085. (408) 737-8181, FAX: (408) 733-7645, e-mail: [email protected], Internet: www.aeroflex-metelics.com.

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