1. Seminar on:
Low Noise Amplifier
Presented by:
Miss Rina Ahire
ME(E&C)
1

2. Contents:
•Low Noise Amplifier
•General philosophy
•Lumped Parameters
•Distributive Parameters
•Matching N/W’s
•Comparison between Narrowband & Wideband LNA

3. Low Noise Amplifier:
• Key component of any low-noise amplifier coming off the antennas
• Signal at that point: weak, good gain & noise performance are necessary

4. General Philosophy:
LNA Design: Two methods
1. Lumped Parameter
2. Distributive Parameter

5. Lumped Parameter:
•Stability, gain & noise analyzed: Bode/ Niquist plots
•During design, active devices & i/p-o/p termination
n/w’s treated separately
•Here voltage & current- Primary variables
-Two port representations(y, z, h or g parameter)

6. Distributive Parameter:
•Considers the distributive nature of the ckts. & uses Smith charts
•Both the active devices & i/p-o/p terminations are consider together
•Power becomes the primary variable of interest
•S-parameter based analysis- main tool

7. Matching Networks:
1. Objectives:
• Provide proper terminations to the Analog filters-
Between antenna & the LNA
Between the LNA & the subsequent mixer
• I/P matching n/w ensures optimum noise performance & stability at the i/p
O/P matching n/w ensures stability at the o/p
• I/P matching n/w: Proper power matching between the antenna & the LNA

8. 2 . Matching for Noise & Stability:
Fig. Generalized LNA topology

9. 3. Matching for Power:
Fig. (a) LNA using
lumped parameter
representation
Fig(b) LNA with
transformer matching
at the i/p

10. Comparisons of Narrowband and Wideband LNA:
Narrowband LNA Wideband LNA
Having tuned matching n/w at Wideband matching n/w for
i/p &o/p frequency response of the
amplifier – flat at the o/p
Circuit is simple Circuit is complicated
Low noise performance Noise performance is poor
Circuit performance is simple Circuit performance is poor
Difficult to achieve bandpass Easy to achieve bandpass
amplification amplification

11. Thank You