Seminar on:

Low Noise Amplifier

Presented by:Miss Rina Ahire

ME(E&C)

1

Contents:

•Low Noise Amplifier

•General philosophy

•Lumped Parameters

•Distributive Parameters

•Matching N/W’s

•Comparison between Narrowband & Wideband LNA

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

General Philosophy:

LNA Design: Two methods

1. Lumped Parameter

2. Distributive Parameter

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)

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

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

2 . Matching for Noise & Stability:

Fig. Generalized LNA topology

3. Matching for Power:

Fig. (a) LNA using lumped parameter representation

Fig(b) LNA with transformer matching at the i/p

Comparisons of Narrowband and Wideband LNA:

Narrowband LNA Wideband LNA

Having tuned matching n/w at i/p &o/p

Wideband matching n/w for 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 amplification

Easy to achieve bandpass amplification

Thank You