Download this article in .PDF format
This file type includes high resolution graphics and schematics.

Noise can block signals in a receiver and limit the lower end of the system’s dynamic range. For that reason, system designers usually specify a front-end low-noise amplifier (LNA) for the receiver with reasonable small signal gain, so as to boost signals from an antenna with extremely low noise figure. Any noise added to the system at that point stays with the system and tends to become indistinguishable from the desired signals, making communications less effective.

Traditionally, LNAs with noise figures approaching 1 dB at RF/microwave frequencies were considered good insurance against noise contamination early in a receiving system. But the model PMA2-33LN+ LNA from Mini-Circuits sets a new mark for noise figure, with typical performance of 0.37 dB noise figure at 900 MHz. The packaged amplifier, which is usable from 400 MHz to 3 GHz, further impresses at the other end of the dynamic range with a third-order intercept point (IP3) of typically +34 dBm at 900 MHz and +40 dBm at 3 GHz.

The model PMA2-33LN+ LNA (Fig. 1) is supplied in a compact, 8-lead, 2 x 2 x 0.55 mm MCLP housing with low inductance and repeatable transitions, providing low-loss thermal connections to a printed-circuit board (PCB). To further support the low noise figure and smooth thermal transitions, the LNA housing incorporates a SnAgNi lead finish.

1. Model PMA2-33LN+ is a packaged GaAs E-pHEMT low-noise amplifier that also boasts high gain and reasonably high output power.

The amplifier is based on the 0.25-μm GaAs enhancement-mode pseudomorphic high-electron-mobility-transistor (E-pHEMT) technology usually associated with high-power or large-signal transistors and amplifiers, but adapted here to low-noise applications. The LNA is designed to operate on a single +3-VDC voltage supply. It provides high reliability with a low operating current of nominally 58 mA across an operating temperature range of -40 to +85°C. On-die electrostatic-discharge (ESD) protection is included in accordance with Class 1A (ESD) requirements [per the 250-V Human Body Model (HBM)].

2. The model PMA2-33LN+ maintains noise figure well below 1 dB across its operating voltages and frequency ranges.

The dynamic range of a communications system can be increased by boosting transmit power or improving the noise figure and sensitivity of the receiver, and it is usually easier to modify the receiver than to boost the power levels of the transmitter. The new LNA should help improve a wide range of receivers. Its noise figure is impressive throughout its operating frequency range (Fig. 2), with typical noise figures of 0.64 dB at 400 MHz, 0.37 dB at 900 MHz, 0.48 dB at 1.5 GHz, 0.58 dB at 2.0 GHz, and 0.86 dB at 3.0 GHz. The amplifier’s small-signal gain (Fig. 3) is 24.0 dB at 400 MHz, 18.7 dB at 900 MHz, 14.5 dB at 1.5 GHz, 12.1 dB at 2.0 GHz, and 8.5 dB at 3.0 GHz.

3. The compact LNA also provides high gain across its wide operating-frequency range.

Download this article in .PDF format
This file type includes high resolution graphics and schematics.