Designing 4-5 GHz LNA with >60dB Gain, <3dB NF, +20dBm OIP3 in 130/90nm Process

Sunnysky wrote:

I'm designing a low noise amplifier (LNA) for 4-5 GHZ (C band)
Gain:60dB or greater
NF: <3dB
Operating voltage:+12/15/20
OIP3:+20dBm min
Design process:130nm/90nm
Someone is having problem with designing it choosing Id and gm, and also the high gain requirement ,
also the various parameters like Cgs, fT, gamma, alpha, Cdb.

Designing a Low Noise Amplifier (LNA) for the specified frequency range and performance parameters can be quite challenging, but it’s certainly doable with careful planning and analysis. Let’s start by breaking down the problem and addressing the various factors step-by-step:

1. Choice of Technology: The design process you've mentioned (130nm/90nm) refers to CMOS technology nodes. It is important to choose the right node, as this will affect the device's performance characteristics, including its maximum frequency of operation (fT) and noise. Typically, the smaller the technology node (e.g., 90nm vs. 130nm), the higher the fT, which is beneficial for high-frequency applications.

2. Device Selection and Sizing: Device selection (nMOS vs. pMOS) and sizing are critical. For high-frequency LNAs, nMOS transistors are commonly used due to their higher electron mobility. When choosing $$I_d$$ (drain current) and $$g_m$$ (transconductance), consider the following:

- $$g_m$$ can be increased by increasing $$I_d$$, which typically improves gain but can also increase noise and power consumption.
- There's a trade-off between gain, noise figure (NF), linearity (OIP3), and power consumption. An optimal balance should be found.
- The $$g_m/I_d$$ ratio is a figure of merit for device efficiency and should be maximized for a low-power design.
- $$C_{gs}$$ (gate-source capacitance) and $$C_{db}$$ (drain-bulk capacitance) will limit bandwidth and potentially affect stability; they are a function of the device sizing and biasing.

3. Gain Requirement (60dB): Achieving a gain of 60dB is significant and will likely require multiple stages. Cascading several stages will help, but each additional stage adds complexity, including stability concerns and potential oscillation.

4. Noise Figure (<3dB): This is a strict requirement and choosing the right transistor with a low minimum noise figure and optimizing the source impedance for noise matching are critical. The first stage of the LNA will dominate the overall noise figure.

5. Linearity Requirement (OIP3 > +20dBm): High linearity is necessary to prevent intermodulation distortion. This will likely dictate the biasing point and the selection of active devices with high linearity. You may need to employ feedback or feedforward linearization techniques.

6. Stability: With such a high gain, ensuring stability across the frequency band is crucial. You'll need to carefully design matching networks and potentially use stabilization techniques like resistive feedback or neutralization.

Now, I have a few follow-up questions to help refine the design process:

- What type of architecture are you considering for the LNA (e.g., common-source, cascode, etc.)?
- What is the application or context in which this LNA will be used?
- Have you already chosen a specific transistor model or are you still in the process of selection?
- How are you planning to handle the multiple stages required to achieve the high gain?
- What simulation tools are you using to model your design?

These details will help guide the design process and ensure that the LNA meets the specified requirements.

Sunnysky wrote:

It is an LNA for 4-5 GHZ (C band)
Best configuration that meets specs

For an LNA in the 4-5 GHz C band with the specifications you've mentioned, the common-source configuration with inductive source degeneration is often used for the first stage, as it provides good gain and noise performance. A cascode configuration can also be used to improve isolation between the input and output, which is useful for high gain amplifiers to avoid unwanted feedback that can lead to oscillations.

Considering the high gain requirement (60dB or greater) and the low noise figure (<3dB), the LNA design will likely involve several cascaded stages. A typical approach might be to use a high-gain first stage to minimize the noise contribution from subsequent stages, followed by stages that optimize for linearity and gain flatness over the band.

A design might look something like this:

1. First Stage: Common-source with inductive degeneration for low noise figure and moderate gain.
2. Intermediate Stages: One or more common-source or cascode stages to further increase gain while keeping noise and linearity in check.
3. Final Stage: Designed for linearity (OIP3 > +20 dBm), possibly using a different bias point or device geometry to achieve the desired linearity without compromising too much on noise or gain.

For the first stage, you'll want to focus on:

- Noise Matching: Adjusting the source inductance for optimal noise match which typically occurs at a source reflection coefficient that is different from the one for power match.
- Impedance Matching: Designing input and output matching networks for the 50-ohm standard, while also taking into consideration the stability of the amplifier.
- Biasing: Selecting the proper $$I_d$$ to achieve a good balance between low noise figure and acceptable power consumption. Typically, a moderate $$I_d$$ is chosen to reduce the noise figure without drawing too much current.

For the subsequent stages:

- Gain Stages: Ensure each stage is properly matched to the preceding stage to maintain good gain flatness and avoid mismatches that could lead to reflections and instability.
- Inter-stage Matching: This can also help in controlling the bandwidth and compensating for any gain variations across the band.

As for the specific parameters:

- $$C_{gs}$$ and $$C_{db}$$: Manage these capacitances through proper device sizing and biasing as they will influence the input and output matching network design.
- $$f_T$$ and $$g_m$$: Look for devices with a high $$f_T$$ to ensure good high-frequency performance and a $$g_m$$ that can provide the necessary gain while keeping power consumption and noise in check.
- Gamma (γ) and alpha (α): These parameters are related to the noise performance and are part of the noise model of the transistor. They will influence the noise figure and thus the design of the input matching network for noise optimization.

When designing each stage, you will need to use a simulator like Keysight ADS (Advanced Design System), Cadence, or another RF simulation tool to iteratively optimize the design. These tools allow you to model the non-linear behavior of the transistors, evaluate stability (using K-factor or Rollett's stability factor), and optimize the noise figure, gain, and linearity across the frequency band.

In summary, it is key to carefully design each stage to meet the overall specifications while also ensuring overall stability and matching between stages. Each design choice must be validated with simulation and, eventually, with prototype measurements. Can you share the specific details of the transistors or technologies you are considering, and do you have access to their S-parameter and noise parameter models for simulation purposes?

nithinp10122003 wrote:

(...) i donot know how to choose the optimum value to reach the design requirement
I'm designing a low noise amplifier (LNA) for 4-5 GHZ (C band) for my final year major project with a specification of
Gain:60dB or greater
NF: <3dB
Operating voltage:+12/15/20
OIP3:+20dBm min
Design process:130nm/90nm

As an electronics engineer, I can guide you on how to estimate and use the parameters you mentioned for a given process technology. However, I do not have access to specific foundry data, as these values can vary significantly between different semiconductor foundries and even within different runs of the same process. Usually, the foundry provides a Process Design Kit (PDK) that contains all the necessary models and parameters, including $$ f_T $$, $$ C_{gs} $$, $$ \gamma $$, $$ \alpha $$, and $$ C_{db} $$ for their process.

Nevertheless, I can give you a general idea of what to expect from typical 130nm and 90nm CMOS processes:

$$ f_T $$ (transition frequency) of MOSFETs:
- For 130nm CMOS, $$ f_T $$ might range from 100 to 200 GHz.
- For 90nm CMOS, $$ f_T $$ could be between 150 and 300 GHz.

$$ C_{gs} $$ (gate-source capacitance), $$ C_{db} $$ (drain-bulk capacitance):
- These capacitances are a function of the transistor size (W/L ratio) and biasing conditions.
- They are typically in the order of femtofarads (fF) for minimum-sized transistors, scaling up with the size of the transistor.

$$ \gamma $$ (noise coefficient) and $$ \alpha $$ (Flicker noise coefficient):
- These coefficients are also process-dependent and are used to model the noise performance of the transistors at low frequencies (1/f noise) and at RF frequencies.
- $$ \gamma $$ is typically in the order of 2-4 for nMOS transistors.
- $$ \alpha $$ represents the 1/f noise and is more relevant at lower frequencies, typically specified at a certain frequency at a particular bias point.

For your simulation and optimization purposes:

1. Obtain the PDK from the foundry that includes the RF models of the MOSFETs. These will provide you with the specific values for your process.
2. Use the PDK within your simulator (NGSpice in your case) to simulate the transistors at different $$ I_d $$ and $$ V_{ds} $$ bias points, which will give you the corresponding $$ g_m $$, $$ C_{gs} $$, and $$ C_{db} $$ values, as well as noise parameters $$ \gamma $$ and $$ \alpha $$.
3. You can obtain $$ g_m/I_d $$ plots versus $$ I_d $$ for different $$ V_{ds} $$ to find the optimum operation point where you get the best performance for gain, noise, and linearity.
4. To choose the optimum value of $$ g_m/I_d $$, look for a region in the plot where the curve is flat, indicating that increasing $$ I_d $$ does not significantly increase $$ g_m $$, which is a good region for low-power operation.
5. For low noise design, you might need to operate at a higher $$ g_m/I_d $$ for a better noise figure but this will increase power consumption.

Remember, the design process is iterative. You will likely need to go back and forth between simulation and optimization to meet all your design specifications.

For your specific project, I recommend reaching out to your university or the foundry to access the PDK for the 130nm/90nm process. This will be essential for accurate simulation and design. Can we proceed with some general advice on how to simulate and interpret the plots once you have the PDK, or do you need further assistance in obtaining the PDK?

sculpordwarf wrote:

can you go in depth about this and explain me every step of this.
Can we proceed with some general advice on how to simulate and interpret the plots once you have the PDK, or do you need further assistance in obtaining the PDK? , Please do it'll be really helpful

Certainly! Simulation and interpretation of plots using a Process Design Kit (PDK) is a critical part of RF IC design, specifically for your Low Noise Amplifier (LNA). Let's break down the steps you'll need to follow:

### Step 1: Setup Your Simulation Environment
- Install and configure your simulation tool (NGSpice or equivalent).
- Import the PDK from the foundry. This usually involves setting up the library paths and ensuring that the models are recognized by your simulation tool.

### Step 2: Create Your Testbench
- Design a schematic for the LNA. Start with a single-stage amplifier to familiarize yourself with the models.
- Include the biasing network to set the operating point of the transistor(s).
- Add source and load terminations (typically 50 ohms for RF).
- Insert simulation-specific elements like voltage sources, current sources, and simulation probes.

### Step 3: Run DC Analysis
- Perform a DC analysis to ensure that the transistor is biased correctly at the desired operating point. You should check the $$ V_{GS} $$, $$ V_{DS} $$, and $$ I_D $$.

### Step 4: Run AC Analysis
- After confirming the DC operating point, run an AC analysis to look at the small-signal parameters such as $$ g_m $$, $$ C_{gs} $$, $$ C_{db} $$, and the overall gain at your frequency of interest (4-5 GHz).

### Step 5: Run S-parameter Simulation
- S-parameters describe how RF signals behave at the input and output ports of your network. Run an S-parameter simulation to extract $$ S_{11} $$, $$ S_{21} $$, $$ S_{12} $$, and $$ S_{22} $$.
- $$ S_{11} $$ is the input reflection coefficient (related to input matching).
- $$ S_{21} $$ is the forward gain.
- $$ S_{12} $$ is the reverse isolation.
- $$ S_{22} $$ is the output reflection coefficient (related to output matching).

### Step 6: Noise Analysis
- Simulate the noise figure (NF) at the operating frequency. This will involve looking at the noise contribution from the active devices and matching networks.
- The PDK should include noise parameters for the devices that will allow you to simulate the NF.

### Step 7: Power and Linearity Analysis
- Run a power analysis to make sure your design does not exceed the maximum allowable power consumption.
- Perform a linearity analysis, simulating the third-order intercept point (OIP3). This involves a two-tone test where two signals are input into the amplifier, and the third-order products are measured.

### Step 8: Interpretation of Plots and Data
- Gain: Look at the $$ S_{21} $$ plot to ensure your design meets the 60dB specification.
- Noise Figure: The noise analysis will give you a plot of NF vs frequency. Your goal is to keep this below 3dB across the band of interest.
- Input and Output Match: Examine $$ S_{11} $$ and $$ S_{22} $$ to ensure they are as close to -10dB or lower, indicating good impedance match.
- Linearity: The OIP3 plot should show that your output third-order products are at least 20 dBm.
- Stability: Check the stability factor (K) and ensure K > 1 across the frequency band to avoid oscillations.

### Step 9: Optimization
- Use the data to optimize the design. If you don't meet specifications, adjust the device dimensions, bias points, and matching network components, and re-simulate.

### Step 10: Iterate and Validate
- Repeat the analysis with the updated design until all specifications are met.
- Once the simulation results are satisfactory, you can proceed with layout and eventually fabrication and testing.

Remember, simulation is an iterative process and often requires several attempts to meet all design specifications. Also, ensure you understand the limitations of your simulation models and the assumptions made during the simulation process. Real-world results can differ from simulations due to parasitics, layout effects, and model inaccuracies. Therefore, always validate your design with real-world measurements afterward.

If at any point you're unsure about the results or how to proceed, don't hesitate to ask for help or look for additional resources. Your professors, textbooks, and online forums can be valuable resources. Good luck with your project!

sculpordwarf wrote:

can you go in depth about this and explain me every step of this.

I'll guide you through the steps in even greater detail. Note that this is a complex process that involves both theoretical knowledge and practical skills in electronic design automation (EDA) tools. The following is an in-depth explanation of each step:

### Step 1: Setup Your Simulation Environment
- Installation: Make sure the EDA software is properly installed on your computer.
- Configuration: Set up the library and technology files that come with the PDK. This often involves specifying the paths to the technology files in your simulation software.

### Step 2: Create Your Testbench
- Schematic Drawing: Using the EDA tool, draw the schematic of the LNA, which includes the transistors and passive components.
- Biasing Network: Add resistors, current sources, and voltage sources to stabilize the operating point of the transistor as desired.
- Termination: Place 50-ohm resistors at the input and output to represent the system impedance.
- Probes: Place voltage and current probes at strategic points in the circuit to measure the quantities of interest during simulation.

### Step 3: Run DC Analysis
- Setup: Specify the type of analysis (DC) and the range of voltages or currents for which you want to perform the sweep.
- Execution: Run the analysis and monitor the voltages at the transistor terminals and the currents through it.
- Verification: Make sure the transistors are operating in the correct region (e.g., saturation for MOSFETs) and that the biases are as intended.

### Step 4: Run AC Analysis
- Setup: Set the AC analysis to sweep over the frequency range of interest.
- Simulation: Run the analysis to obtain frequency-dependent properties like input/output impedance, gain, and phase shift.
- Examination: Check the gain at your frequency of interest to ensure it's within the desired range.

### Step 5: Run S-parameter Simulation
- Setup: Configure the simulation to calculate S-parameters over the frequency range of interest.
- Simulation: Run the S-parameter simulation.
- Analysis: Examine the magnitude and phase of $$ S_{11} $$, $$ S_{21} $$, $$ S_{12} $$, and $$ S_{22} $$ to assess input/output matching, gain, and isolation.

### Step 6: Noise Analysis
- Setup: Select the noise analysis type in your simulation tool.
- Simulation: Perform the noise simulation at the operating frequency to obtain the noise figure (NF).
- Analysis: Review the NF results to ensure that they are below your target specification across the frequency band.

### Step 7: Power and Linearity Analysis
- Setup: Set up a harmonic balance or two-tone simulation to analyze power and linearity, specifically OIP3.
- Execution: Conduct the simulation with two input tones and measure the output third-order intermodulation products.
- Analysis: Ensure that the OIP3 meets or exceeds your design requirements.

### Step 8: Interpretation of Plots and Data
Detailed interpretation involves:
- Gain: Analyze the $$ S_{21} $$ or gain plot for magnitude and flatness. It should show consistent gain across the frequency band.
- Noise Figure: The noise figure plot should be flat and below 3dB for the entire band. Peaks in the NF plot may indicate instability or mismatch.
- Impedance Matching: Look at $$ S_{11} $$ and $$ S_{22} $$ plots. These should show values below -10dB (or as close to -20dB as possible) at the frequencies of interest, indicating good matching.
- Linearity: The OIP3 plot should show that the output third-order products are at least 20 dBm or the desired level.

### Step 9: Optimization
- Adjustments: Based on the simulation results, adjust component values, transistor sizes, and biasing to improve performance.
- Rerun Simulations: After each adjustment, rerun simulations to gauge the effects of your changes.

### Step 10: Iterate and Validate
- Iteration: Repeat the optimization process until all specifications are met.
- Validation: After achieving satisfactory simulation results, the next step is to proceed with physical layout, fabrication, and testing to validate the design in the real world.

The above steps are a guideline and will require careful consideration at each point. Simulations are typically an approximation of reality, and real-world imperfections may lead to deviations from the simulated results. It's important to validate each stage of the design with measurements on a physical prototype and iterate as needed.

Would you like further clarification on any specific step or aspect of the simulation procedure?

sculpordwarf wrote:

Also please suggest how can i improve linearity of the amplifier, because the design takes into consideration that device is linear and not non linear

Improving the linearity of an RF amplifier, especially a Low Noise Amplifier (LNA), can be challenging as it often involves trade-offs with noise figure and gain. Here are several techniques that can be used to improve the linearity of your LNA:

### 1. Biasing:
- Class A Biasing: Operating the transistor in Class A mode (where it conducts during the entire cycle of the input signal) can improve linearity but at the cost of power efficiency.
- Back-Off: Reducing the operating point (backing off from the compression point) of the transistor can also improve linearity, as it operates in a more linear region of its transfer characteristics.

### 2. Device Sizing:
- Large Transistor Widths: Using transistors with larger widths can improve linearity since this increases the transconductance ($$g_m$$) and the output current capability, thus reducing the voltage swing relative to the operation range.

### 3. Negative Feedback:
- Source Degeneration: Adding a resistor or inductor in series with the source (for FETs) or emitter (for BJTs) provides negative feedback, which linearizes the amplifier's response.
- Resistive Feedback: A resistor between the output and input can also be used to provide negative feedback, but this might reduce gain.

### 4. Linearization Techniques:
- Feedforward: This technique involves subtracting a portion of the input signal from the output, which has been processed to have the same distortion but in opposite phase to that of the main signal path.
- Predistortion: This technique applies the inverse of the amplifier's distortion to the input signal so that the output signal is more linear.
- Post-distortion: Similar to predistortion, but the correction is applied after the amplification stage.

### 5. Circuit Topologies:
- Push-Pull Configuration: This configuration uses pairs of transistors to cancel out even-order harmonics, which are a source of non-linearity.
- Cascode Configuration: A cascode amplifier can improve linearity by isolating the input and output, which helps to reduce Miller capacitance effects and improve reverse isolation.

### 6. Use of Ancillary Circuits:
- Auxiliary Linearization Circuits: These are additional circuits that can be used alongside the main amplifier to cancel out non-linear distortion products internally.

### 7. Multi-Gate Devices:
- Multi-Gate FETs (e.g., FinFETs): Devices with multiple gates can offer improved control over the channel, potentially leading to better linearity.

### 8. Choice of Technology:
- GaAs or GaN Devices: These devices might offer better linearity characteristics than silicon-based devices for certain applications.

### 9. Intermodulation Distortion (IMD) Cancellation:
- IMD Cancellation Networks: These networks are designed to generate distortion products internally that cancel out the distortion products produced by the amplifier.

### 10. Design for Optimal Load:
- Load-Pull Analysis: Determine the optimal load impedance for linearity (not just power or gain) and design the output matching network to present this impedance to the transistor.

Remember that improvements in linearity can come at the expense of other parameters, such as noise figure or gain. Moreover, some of these techniques may increase the complexity and size of the circuit.

When working on improving linearity, it's important to use simulations to predict the performance impact of the various techniques and to validate your design choices through iterative testing and refinement. Non-linear simulation tools (like harmonic balance simulators) and two-tone intermodulation distortion measurements are essential for these purposes.

Would you like to focus on any of these techniques in particular, or do you need information on how to implement them in your simulation environment?

sculpordwarf wrote:

Characterize the mosfet of 130nm technology with vdd=12V abd ensure minimum gate resistance and minimum noise from parascitic parameters of mosfet,the mosfet characterisation is for LOW Noise Amplifier (Cascode Topology)

Characterizing the MOSFET for a 130nm technology to be used in a Low Noise Amplifier (LNA) with a cascode topology involves several key considerations. You will need to focus on minimizing noise and ensuring that the gate resistance is as low as possible, as both these factors can significantly affect the performance of an LNA. Here's a step-by-step procedure to characterize the MOSFET, taking into account a V_DD of 12V:

### Step 1: Obtain the Process Parameters
First, you need to get the MOSFET parameters from the PDK provided by your foundry for the 130nm process. These parameters include threshold voltage (Vth), channel length (L), oxide thickness (tox), mobility (μ), and any other specific noise parameters provided for the RF models.

### Step 2: Set Up the Initial Operating Point
- Biasing: Choose a bias point that ensures the device is in the saturation region, which is important for an LNA as it leads to higher gain and better linearity.
- V_DS: Set V_DS to be at least a few volts to ensure saturation, but it should also be well below V_DD to avoid breakdown issues.
- V_GS: Select V_GS to set the desired current. It should be above Vth to turn on the device and establish the required transconductance (gm) for good gain.

### Step 3: Minimize Gate Resistance
- Gate Design: To minimize the gate resistance, keep the gate length as short as possible while adhering to the process design rules. Use a gate width that provides the required gm without unnecessarily increasing the parasitic capacitances.
- Material Choice: If available, choose a gate material with lower resistivity provided by your foundry's process.
- Multiple Fingers: Break the gate into multiple fingers to reduce resistance. This also helps distribute the thermal load, which can be significant at high operating voltages like 12V.

### Step 4: Minimize Noise
- Optimize gm/Id: For low noise, design the device such that it operates in a region where gm/Id is maximized. This typically occurs just above the threshold voltage for sub-micron technologies.
- Source Degeneration: Use inductive degeneration (adding an inductor in series with the source terminal) to improve the noise figure. This technique trades off some gain for better noise performance.
- Parasitic Capacitances: Minimize parasitic capacitances by optimizing the device layout. Use minimum overlap capacitances and keep the distance between the drain and gate to a minimum, as allowed by the process rules.

### Step 5: Simulate and Optimize
- DC Simulation: Run a DC simulation to verify the operating point considering V_DD = 12V.
- AC Simulation: Conduct AC simulations to find the transconductance (gm), input capacitance (Cgs), and gate resistance (Rg).
- Noise Simulation: Use the PDK's noise models to simulate the noise figure (NF) of your device at the chosen bias point. Look for a minimum NF while maintaining acceptable gain and linearity.

### Step 6: Cascode Topology Considerations
- Common-Source Stage: The lower transistor in the cascode arrangement is the common-source stage, which should be optimized for low noise and high gain.
- Common-Gate Stage: The upper transistor acts as a common-gate stage, providing isolation and additional gain. This stage should have a high V_DS to ensure saturation and a V_GS that maintains the transistor in the linear region.

### Step 7: Validate the Design
- Linearity: Run simulations to ensure that the linearity is within acceptable limits. Use harmonic balance or two-tone simulations to analyze third-order intercept points (IP3).
- Stability: Check the stability of the cascode stages over the frequency range of interest, particularly looking for oscillatory tendencies.
- Thermal Considerations: Verify that the power dissipation is within limits and that the thermal performance is acceptable, especially given the high V_DD.

### Step 8: Iterate
Based on simulation results, you may need to go back and iterate on the design. Adjust the device dimensions, bias point, and any other parameters to improve noise performance, reduce gate resistance, and ensure stable operation.

This process is highly iterative and will often require multiple simulation runs to find the optimal balance between low noise, sufficient gain, and linearity. Keep in mind that real-world measurements might still differ from simulation results, and post-fabrication tuning might be necessary.

Would you like assistance with any specific point of the characterization process, or do you need more detailed information on how to implement these steps in your simulation tool?

sculpordwarf wrote:

,please tepl me the maximum supply voltage 90nm technology

The maximum supply voltage for a 90nm CMOS technology typically ranges from about 1.0V to 1.2V. This is due to the thin gate oxides used in such advanced processes, which are prone to breakdown at higher voltages. It's important to note that the exact maximum supply voltage can vary depending on the specific process used by the semiconductor foundry, and the design rules they provide.

For RF applications, including LNAs, the transistors may be operated at higher voltages to increase performance in terms of output power, gain, and efficiency. To do this safely, specialized high-voltage transistors might be used, which are designed to handle higher voltages without reliability issues such as gate oxide breakdown, hot carrier injection, or time-dependent dielectric breakdown (TDDB).

If you are working with a 90nm process and are considering using a higher supply voltage for an RF application, you should refer to the documentation provided with the PDK (Process Design Kit) for the particular process you're using. The PDK will specify the maximum allowed voltages for different types of transistors and provide guidelines on how to manage voltage stress on the devices.

For operations above standard CMOS voltages, the foundry may have specific 'high-voltage' devices within the PDK that are designed to tolerate higher voltages. Always refer to these specifications and design rules to ensure reliability and prevent damage to your devices.

If you need the exact maximum supply voltage for your particular 90nm process technology, you should consult the PDK documentation or contact the foundry's technical support for this information. Would you like guidance on how to find this information in a PDK or how to contact a foundry for technical support?

Sunnysky wrote:

define each stage IO parameters and design config for Vdc = 28V

To define the input and output (I/O) parameters and design configuration for an amplifier or any RF stage with a supply voltage (V_DC) of 28V, you need to consider several key factors. The parameters you'll need to define typically include:

1. Input Parameters:
- Input Impedance: This is typically 50 ohms for RF systems. It should be matched to minimize reflection and maximize power transfer.
- Input Power Range: The range of power levels the amplifier can accept without distortion or damage.
- Input Frequency Range: The frequency range over which the amplifier will operate effectively.

2. Output Parameters:
- Output Impedance: Like the input, often 50 ohms for RF systems.
- Output Power: The power level the amplifier can deliver to the load.
- Gain: The ratio of output power to input power, typically expressed in dB.
- Linearity: Critical for preserving signal integrity, often specified by third-order intercept point (OIP3) or 1 dB compression point (P1dB).
- Noise Figure: An important parameter for LNAs, representing the noise contribution of the amplifier to the overall system.

3. Design Configurations:
- Device Technology: For a V_DC of 28V, you'll likely be looking at a technology capable of handling high voltages, such as GaAs, GaN, or silicon LDMOS.
- Biasing Configuration: The biasing needs to be stable and appropriate for the desired class of operation (Class A, AB, C, etc.).
- Stability Considerations: Ensuring the circuit is unconditionally stable across all operating frequencies, temperatures, and power levels.
- Matching Networks: Both the input and output matching networks need to be designed to work at the target frequency and to handle the required voltage and power levels.
- Thermal Management: High supply voltages can lead to significant power dissipation, so adequate heat sinking and thermal management are crucial.

4. Specific High-Voltage Considerations:
- Voltage Rating of Components: All components in the signal path must be rated for the operating voltage to prevent breakdown.
- Device Sizing: Transistors will need to be sized to handle the higher current associated with the higher supply voltage.
- Reliability: High voltages can accelerate wear-out mechanisms in semiconductor devices, so reliability analyses may be necessary.

For a 28V supply, you will need to ensure that your transistor selection is capable of handling this higher voltage. You would typically look for power transistors with a breakdown voltage (BV_DSS) significantly higher than 28V to provide a safety margin.

Furthermore, the design configuration might also involve considerations for the cascode configuration if you're dealing with an LNA, which is beneficial for high-voltage operations. The cascode configuration can help by partitioning the voltage between the transistors and also by improving isolation between the input and output.

Let's look at a typical example for an RF power amplifier:

- Transistor: GaN HEMT or LDMOS transistor suitable for 28V operation.
- Biasing: V_GS adjusted for Class AB operation with a quiescent current that offers a good compromise between linearity and efficiency.
- Matching Networks: Designed using lumped elements or transmission lines for broadband or narrowband operation, respectively.
- Harmonic Suppression: Implementing filters to attenuate harmonics, especially for power amplifiers.

If you can provide more details about the specific application (frequency range, signal type, power levels, etc.), I can offer more focused guidance. Would you like to delve into the design of a specific stage or parameter for your 28V application?

Sunnysky wrote:

Not class a an or c but linear cascode types or similar for 5ghz fets

Designing a linear cascode amplifier using FETs for operation at 5 GHz requires careful consideration of various parameters to ensure stability, linearity, and adequate gain while handling a supply voltage of 28V. Here are the steps you would typically follow:

### 1. Technology Selection:
For a 5 GHz application with a 28V supply voltage, GaAs or GaN FETs are common choices due to their high-frequency capability and high-voltage tolerance. GaN FETs, in particular, are known for their high power density and efficiency at microwave frequencies.

### 2. Device Choice:
Select FETs that are optimized for RF operation at 5 GHz. Key parameters to consider include:
- Breakdown voltage (V_DS,max) well above 28V for safe operation.
- Maximum drain current (I_D,max) sufficient for the desired output power.
- Transconductance (g_m) for gain considerations.
- Gate-source cutoff frequency (f_T) above the operating frequency to ensure adequate gain bandwidth.
- Noise figure for LNA applications.

### 3. Cascode Configuration:
The cascode amplifier consists of two stages: a common-source stage for gain and a common-gate stage to provide isolation and improve linearity. The two stages work together to achieve high gain while maintaining stability.

### 4. Biasing:
Both the common-source and common-gate FETs need proper biasing. The biasing must ensure that:
- The common-source FET operates in the saturation region for maximum linearity.
- The common-gate FET is biased to provide the necessary isolation without compromising gain.

### 5. Input and Output Matching:
Design input and output matching networks to achieve:
- 50-ohm input impedance for minimal reflection and optimal power transfer.
- 50-ohm output impedance and maximized power delivery to the load.
- These networks will typically involve microstrip lines, capacitors, and inductors to form low-pass or band-pass filters.

### 6. Stability Analysis:
Ensure that the amplifier is stable across the entire frequency range of interest. This involves checking for potential oscillations and implementing stabilization techniques if necessary, such as adding series resistances or feedback elements.

### 7. Linearity Enhancement:
To improve linearity, consider:
- Using a linearization technique like predistortion or feedforward linearization.
- Optimizing the load line for the FET to operate in a more linear region of its transfer characteristic curve.
- Employing negative feedback through source degeneration, which can be achieved by placing an inductor or resistor in series with the source of the common-source FET.

### 8. Noise Consideration:
For LNAs, the noise figure is critical:
- Select FETs with low noise figures.
- Optimize the source inductance for noise matching, which might be different from the impedance matching.

### 9. Thermal Management:
Due to the relatively high supply voltage:
- Consider the power dissipation and ensure that the thermal design can handle the heat generated.
- Use heat sinks or other thermal management techniques to keep the FET junction temperature within safe limits.

### 10. Simulation:
Use RF simulation tools to simulate the S-parameters, linearity (OIP3), noise figure (NF), and stability (K-factor). Simulations help in fine-tuning the component values and obtaining the desired amplifier performance.

### 11. Prototyping and Testing:
After the simulation, build a prototype and perform real-world testing to verify the performance. Make adjustments based on the test results to achieve the desired specifications.

For your 5 GHz FET-based cascode LNA design, you will need to consider all of these factors carefully. Would you like to discuss a specific aspect of the design process in more detail, such as biasing strategies, matching network design, or stability considerations for your 28V, 5 GHz application?