Choose an Appropriate Active Device

• Select a low-noise transistor (BJT, HEMT, or FET) from the ADS library.
• Check its S-parameters, Noise Figure (NF), and stability factor (K).2. Bias the Transistor Correctly
• Use DC simulation to set proper bias point (Vgs, Vds, or Vce, Ic).
• The gain varies significantly with bias — optimize for maximum Gmax or GA

In ADS:

• Use DC simulation block and sweep Vgs/Vds to find optimal bias point.
• Check S-parameter results at each bias point.

Is the device unconditionally stable? If so, simultaneous conjugate match will achieve Gmax. If not and you desire to improve gain and if the percentage bandwidth is not to excessive, then consider adding neutralization.

Alan Victor Sir, could you please explain the procedure to implement neutralization in an LNA design to enhance gain and stability?"

Let me know if you'd like a follow-up sentence asking for examples in ADS.

Neutralization is a circuit technique to mitigate unwanted feedback, usually capacitive between drain and gate in MOS or FET devices. The instability due to positive feedback can manifest in oscillations introduced by inappropriate source or load Z values. One technique is to consider a topology, like the cascode, to significantly reduce this feedback. Another is incorporate deliberate negative feedback to offset the gate-drain positive feedback. A C is added, embedded, in the output matching structure and tied back to the gate node. Details and a review of the topics are found in

Neutralization Techniques for High-Frequency Amplifiers: An Overview

An IEEE publication paper.

You can get a good handle on what technique works best for your design by exploring the S12 or Y12 parameters in simulation of the composite design. Also consider looking for discussions on the topic of unilateral design techniques for amplifiers. Note the difference between neutralized and unilateral designs.

To improve the available gain in LNA design using ADS, you can focus on maximizing power transfer and minimizing reflections by optimizing input and output matching networks. This involves carefully selecting components and biasing conditions to achieve the desired gain while maintaining stability.

I further suggest you start out with a discrete device that is well characterized. Two port scattering parameters which must include a family of noise parameters is essential. The entire data set will be in a touchstone file format readily brought into ADS or any similar CAD simulator. The technique of plotting gain and overlaying noise contours will provide insight into the proper topology for device terminations on input and output. Stability should be insured over the band(s) of interest and the nature of any feedback added must be checked to mitigate potential noise figure degradation.