Five Common Methods for LNA Stabilization

1. Input resistive loading: One major and obvious drawback - degrades NF of the LNA and is almost never used.
2. Output resistive loading: Should be carefully used because the effects are lower Gain and lower OP1dB.
3. RLC feedback at the Collector to Base: This is to lower the gain at the lower frequencies and therefore improve the stability.
4. Filter matching network at the transistor's output: The objective is to decrease the gain at a specific frequency or narrowband. This method is frequently used for eliminating gain at high frequencies, far above the operating band. Short circuit quarter wave lines designed for problematic frequencies, or simple capacitors with the same resonant frequency as the frequency of oscillation (or excessive gain) can be used to stabilize the circuit.
5. Emitter feedback inductor: A small inductor/inductance can stabilize the circuit at higher frequencies. However, excessive source inductance will cause the K-factor at higher frequencies falls bellow unity. This effect limits the amount of source inductance that can safely be used.