Building simple Opamp-based amplifiers is not a big issue – as frequencies get higher, things start to become hairy. Analog Devices offers a dedicated amplifier for signals living in the 5.5 to 8.5GhZ bands.

Let us start off with the RF mumbo-jumbo: our part provides 28 dB of gain, 44 dBm output IP3, and 36.5 dBm of saturated output power at 30% PAE from a 7 V power supply. The interesting aspect is that this amount of gain is both temperature and frequency stable – figure one, taken from the HMC1121 datasheet, shows the values you can expect.

The HMC1121’s amplification factors stay constant over a wide range of frequencies

From a technical point of view, getting started with this RF amplifier chip is not too difficult. The HMC1121’s input and output impedances are both 50 Ohms, which means that the chips can find a home in almost every RF design. Furthermore, most power splitters and power combiners work with 50 Ohms – a fact which greatly simplifies combining multiple HMC1121s into a super- HMC1121.

Sadly, the extremely popular HMC1121LP6GE is not easy to solder by hand – the case name stands for 40-Lead Lead Frame Chip Scale Package, which is a tiny part with an edge length of less than 6mm. Fortunately, the EV1HMC1121LP6G evaluation kit is available for getting started.

Another common issue involves the power supply. As the part consists of multiple amplifyer stages, powering it on requires an elaborate switching sequence to prevent lock-ups between ready and booting parts.

Powering the HMC1121 is pretty tedious

Author: Tam Hanna
Published: March 9, 2021