Low noise amplifier design

[APPUARPITA]

Hi,

I have some doubts regarding the design of LOW noise amplifier in MMIC :

I have two PDKs libraries of foundries; one is having PHEMT using Enhancement mode and other is having PHEMT using Depletion mode ( My frequency of operation is Ka-band), which device (E-PHEMT or D-PHEMT)shall i use for the design of low noise amplifier( NF: 1.8 dB with a gain of 25dB.

2. Since the advantage of E-PHEMT(Ehancement mode ) is the single supply that is clearly seen, even though all the commercial available LNAs are being designed using D-PHEMT, can any body explain me the advantages and disadvantages of both types of PHEMT in terms of design of LNA and amplifiers..., i will be very grateful.

3.Also i have a doubt while designing the matching network,ie,movement on the smith chart.Towards the load (anti clock wise rotation on the chart) or towards generator (clockwise rotation on the chart)
i have to match the gamma optimum with the generator impedance for low noise, which way i have to rotate on the smith chart ?

4. Is it better to use a discrete device LNA before MMIC LNA for better noise figure ?

i am waiting for the explaination of these doubts and these will help me further in my design.

 

[attomaz]

hello Mr. Your problem were solved? share your experience.... Cheers,

 

[BigBoss]

E-Type pHEMT Transistors needs positive Vgs but when you check gm curve ( Ids vs Vgs) you will see that it's pretty steep.
** Controlling Vgs value for a single operating point is pretty difficult due to thermal drift for E-Mode pHEMT.Using a negative feedback to stabilize Ids may create more noise.
** E-mode is more nonlinear compare to D-Type pHEMT but E-Mode has larger gm compare to D-mode
** You have find Zopt point and design a appropriate matching circuit for this impedance as usual.

 

[attomaz]

dear, but, isn't clear. I want to do a LNA. But, I found two LNA transistor. A MMIC and another standard transistor. How can I start it using ADS? With only S-par from (s2p) are possible? Able to check NF, gain and Smith C. circles?

 

[BigBoss]

dear, but, isn't clear. I want to do a LNA. But, I found two LNA transistor. A MMIC and another standard transistor. How can I start it using ADS? With only S-par from (s2p) are possible? Able to check NF, gain and Smith C. circles?

For Small Signal Design Metrics, s-parameters ( including Noise Parameters ) are sufficient.It's you who will decide which one will work better.
If you can design an LNA carefully with discrete components, it may be better than MMIC but no guaranteed..
Don't forget Non-linearity too.You will need a nonlinear model of the active devices.

 

[attomaz]

BigBoss, thank you for your help me.
But, s-parameters has included Noise Parameters? I've been using Qorvo trans.
Where could I find Non-linearity model from the device/transistor in this case, right?

 

[BigBoss]

BigBoss, thank you for your help me.
But, s-parameters has included Noise Parameters? I've been using Qorvo trans.
Where could I find Non-linearity model from the device/transistor in this case, right?

Some s-parameter files don't have Noise Parameters so you should request from the manufacturer.
Nonlinear model should also be requested from manufacturer.Some companies don't supply nonlinear models ( s-parameter file too ) unless you request
officially through a company or an university..