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The amplifier’s output characteristics, such as output power at 1-dB compression and output third-order intercept point (OIP3), are quite respectable for an amplifier that also helps enhance receiver sensitivity. The specified output power at 1-dB compression is +21 dBm at 2 GHz, and the measured performance remains flat above +20 dBm from 0.5 to 5.0 GHz (Fig. 4). The measured OIP3 is +34.8 dBm at 2 GHz (data not shown) and +35.2 dBm at 5 GHz with the amplifier active. It is better than +50 dBm at 2 GHz in bypass mode and better than +44 dBm at 5 GHz in bypass mode.

LNA Includes Bypass Protection, Fig. 4

The LVA exhibits good return-loss performance without additional external matching components (Fig. 5). It achieves typical input return loss of 15.5 dB at 1 GHz, 15.0 dB at 3 GHz, 21.2 dB at 4 GHz, and 15.7 dB at 5 GHz. The typical output return loss is 15.5 dB at 1 GHz, 20.4 dB at 2 GHz, 14 dB at 3 GHz, 10.7 dB at 4 GHz, and 9.7 dB at 5 GHz.

LNA Includes Bypass Protection, Fig. 5

To evaluate stability and performance drift that might result from being in the presence of high-level input signals, the amplifier was tested before and after exposure to input signals at 10-dB higher than the rated 1-dB compression point. No change in current from the nominal 80 mA at +5 VDC was found at 100 MHz, 3 GHz, or 6 GHz, using input test power levels of +4.16 dBm at 100 MHz, +1.06 dBm at 3 GHz, and +1.85 dBm at 6 GHz. Testing for variations in gain, noise figure, and current—according to the HBMs at 250 and 500 V—also revealed minimal drift of less than 10%, with only 0.13-dB drift in gain per the HBM at 250 and 500 V, only 0.07-dB drift in noise figure, and no drift (0 mA) in current when the amplifier was tested per the 250- and 500-V HBMs.

This bypass LNA allows the active amplifier circuitry to be protected during high-input-signal conditions and to reduce current consumption in communications systems during particular operating conditions. The amplifier’s consistent gain and noise profiles in active and bypass modes imply that a shift from amplified operation to bypass mode can occur without a dramatic change to the system’s power consumption profile. The amplifier is a candidate for any number of mobile applications, including receivers in WiMAX and WLAN systems. In a WLAN network, for example, a bypass mode can be applied to avoid near-field distortion. P&A: $1.28 each (1000 qty.).

Mini-Circuits, P.O. Box 350166, Brooklyn, NY 11235-0003; (718) 934-4500, FAX: (718) 332-4661.

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