A 500 MHz to 6 GHz Dual, Ultra Low Noise, High IP3 Amplifier

A new GaAs dual low noise amplifier (LNA) that combines high gain and state-of-the-art noise figure with high IP3 performance and is ideal for balanced amplifier use has been introduced. The CDQ0303-QS dual amplifier uses GaAs pseudomorphic high electron mobility transistor (PHEMT) device technology and is designed to cover the 500 to 6000 MHz frequency bands. The device features a gain of 25 dB at 900 MHz and 21 dB at 1900 MHz with noise figures of 0.6 and 0.7 dB at the two frequencies, respectively. In addition, the device offers a high IP3, achieving 31.8 dBm at 900 MHz and 32.5 dBm at 1900 MHz.

Using a distinctive in-house GaAs fabrication process, the two co-located transistor die are assembled in a 4 × 4 mm QFN package, which is a low cost, surface-mount, 16-terminal plastic package that is lead free. Packaging a matched pair of ultra low noise devices in a single package makes the CDQ0303-QS an ideal product for balanced amplifier implementation. The device is intended for applications in the 900 to 2400 MHz frequency range and can also be used in a dual-band configuration where a single transistor is used for each frequency band.

Performance

Figure 1 shows the amplifier’s typical pulsed IV curves and Figure 2 shows its gain and noise figure vs. bias performance. In addition, the device features a 17 dBm P1dB and 33 dBm OIP3 at 2 GHz, as shown in Figure 3. The devices are designed for 3 V DC supply voltage operation with a typical 50 mA operating current for each side of the matched pair of transistors in a recommended application circuit. The individual amplifiers have a 600 mm gate width and a 50 W output impedance and feature excellent uniformity with a 10-year MTBF lifetime.

Fig. 1 Typical pulsed I-V performance (Vgs = –0.2 V per step).

Fig. 2 Noise figure (NF) vs. bias at (a) 1 and (b) 2 GHz.

Fig. 3 OIP3 and P1dB vs. frequency and temperature at Vds = 3 V and Ids = 20 mA.

In addition to the balanced amplifier application, these devices are a perfect solution for the first and second stages of a base station LNA due to the excellent combination of low noise figure and linearity. They are also well suited as medium power driver stages in pole-top amplifiers and other transmit functions, particularly as the low thermal resistance allows extended power dissipation when the voltage and current are adjusted for increased power and linearity.