College of Engineering
Electrical Engineering department
EE407: Electronic Communication Circuits
Project Report
Project Title
Student’s Name
Instructor’s Name
Low Noise Amplifiers: Design & Analysis
Saleh Alfouzan – 441102422
Dr. Abdullah Alghaihab
Table of Contents
Page Number
Circuit Design
3
Transient Response
4
AC Response
5
DC Sweep
6
Noise Response
7
S11 near resonance frequency
9
2
Circuit Design
Figure 1: LNA circuit diagram, LTspice.
This is the circuit configuration for the LNA that will be analyzed for this project, it’s
required to obtain the following responses:
Transient (Input and Output)
AC (Input and Output)
DC Sweep (Input vs Output)
Noise (input referred and output referred)
Input port S11 near resonance frequency.
This circuit achieve a resonance frequency of 4.5GHz, a value of 15nH for L1, 50fF for
Cgs and 10nH for Lg was chosen to achieve this frequency by using the formula:
𝑓𝑟𝑒𝑠 =
1
2𝜋√𝐶𝑔𝑠 (𝐿𝑠 + 𝐿𝑔 )
=
1
2𝜋√50𝑥10−15 (15 + 10)𝑥10−9
3
≈ 4.5𝐺𝐻𝑧
Transient Response
Figure 2: Transient Response
An Input of a sine wave with an amplitude of 0.2V at the resonance frequency of 4.5Ghz
was placed as previously shown in Fig.1.
Figure 3: Transient Response Analysis
As shown in in Fig.3, Vin(p-p)=400mV, Vout(p-p)=894mV.
The gain (Vout/Vin) = 2.24.
To see how the LNA would behave if the frequency changed, the input signal was put
6.5GHz and 2.5GHz respectively, Fig.4 contains the response for each frequency
Figure 4(a): Vout At 6.5GHz = 262.6mV.
Figure 4(b): Vout at 2.5GHz = 133.7mV.
4
AC response
Figure 5: AC response.
the peak gain of 8.73dB occurs at approximately 4.55 GHz, which is close to the resonant
frequency. The steepness of the curve is caused by the resistor of 10ohm that was placed
with L3 as previously shown in Fig.1. this resistor also decreased the peak gain in favor
of stability. Shown in Fig.6, the response without the resistor.
Figure 6: AC response, Without R3
5
DC Sweep
Figure 7: DC Sweep Response, -5V to 5V.
The DC sweep response suggests that the amplifier is operating within its linear range,
where the output voltage is not significantly affected by variations in input voltage.
6
Noise Response
Figure 8(a): Output Referred Noise.
Figure 8(b): Input Referred Noise.
7
In the Output referred noise plot, Fig 8(a), the noise spectral density reaches
approximately 4.956 nV/√Hz around the resonance frequency of 4.5GHz. This peak
signifies that around the resonant frequency, where the gain of the amplifier is at its
maximum, the noise figure of the amplifier is also increased.
While in Fig 8(b) in the Input referred noise, the noise spectral density is the lowest
around the resonance frequency, this is because of the input matching network being
optimized for this frequency (4.5GHz).
8
S11 Near Resonance Frequency
Figure 9: S11 Parameter Near Resonance
9