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Integration is a goal for many wireless electronic products, with more and more capabilities being packed into ever-smaller equipment housings. When it makes sense, multiple functions can be incorporated into a single component housing to save space in the final product design. Such is the case with the model TSS-53LNB+ low-noise amplifier (LNA) from Mini-Circuits.

This compact surface-mount unit doesn’t just incorporate an amplifier capable of high gain and low noise figure from 0.5 to 5.0 GHz: It also provides a switchable bypass circuit, which can be selected in the presence of large signals to avoid overdriving the LNA’s sensitive input port. As with any of the firm’s products, the amplifier is extremely competitively priced for use in a wide range of multiple-tuner and other wireless-communications applications.

The model TSS-53LNB+ LNA (Fig. 1) is based on a 0.25-μm enhancement-mode GaAs pseudomorphic-high-electron-mobility-transistor (pHEMT) semiconductor process. It uses a Darlington cascode configuration to achieve flat gain across a wide bandwidth, with reliable operation from a standard +5-VDC supply. It typically draws about 80 mA current from that supply, and the amplifier is also enabled by means of a +5-VDC voltage.

LNA Includes Bypass Protection, Fig. 1

The bypass LNA is usable from 0.5 to 5.0 GHz, with 21.5-dB typical gain at 2 GHz and 1.3 dB typical noise figure at 2 GHz. It provides +21-dBm typical output power at 1-dB compression at 2 GHz—with ±0.7 dB flat gain from 700 to 2100 MHz—with no matching components.

The amplifier circuitry is powered down in bypass mode to conserve power. The LNA was designed with input and output impedances as close to 50 Ω as possible so that additional external impedance-matching components would not be required for optimum performance. Suitable for test-and-measurement and wireless-communications applications, the RoHS-compliant bypass LNA is supplied in a surface-mount 12-lead 3 × 3 mm MCLP package complete with on-die electrostatic-discharge (ESD) protection, per Class 1A requirements [of the 250-V Human Body Model (HBM)]. The package boasts Sn-Ag alloy over Ni lead finish for good thermal performance over a wide operating temperature range (-40 to +85°C).

The amplifier’s performance was characterized in both normal amplifier and bypass modes using a model PNA-X RF/microwave vector network analyzer (VNA) from Agilent Technologies. The amplifier was found to be extremely stable, with better than 30 dB isolation from about 300 to 6100 MHz (sufficient bypass isolation is critical to achieving high amplifier stability). Arguably as impressive as the amplifier’s flat gain across frequency—typically about 21.5-dB gain at 2 GHz, with gain flat within ±0.7 dB from 0.7 to 2.1 GHz—is the amplifier’s response in bypass mode (Fig. 2), in which the gain/loss is flat within a fraction of a decibel below 0 dB from 0.5 to 5.0 GHz.

LNA Includes Bypass Protection, Fig. 2

Similarly, the amplifier delivers impressive noise-figure performance (Fig. 3) in both active and bypass modes. With the amplifier active, the noise figure reaches about 1.2 dB at 1 GHz and 1.3 dB at 2 GHz, with about 1.5 dB noise figure at 3 and 4 GHz, and peaking at a level of about 1.8 dB at 5 GHz. In the bypass mode, the noise figure remains below its rated specification for the full operating bandwidth. The measured noise figure in bypass mode is a low 0.7 dB at 1 GHz and 0.9 dB at 2 GHz, with noise figure of about 1.0 dB at 3 GHz—reaching only 1.4 dB at 4 GHz and 1.1 dB at 5 GHz.

LNA Includes Bypass Protection, Fig. 3

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