How to choose the proper kind of transistor before IC design

[Alex_Zhan]

Hello everyone, I want to consult you that how to choose a proper kind of transistor before your design. For example, if I want to design a PA, should I choose NMOS or NMOS_rf transistor? How about the voltage? I designed IC before, but choose the same transistors which my friends used. While I change to a new process now. Can anyone help me? Thank you deeply!

 

[MahmoudHassan]

-- If you are using a new process the first step is to check the documentation files
These files have all details about the available devices and standard voltage that can be applied and also the layout rules and so on
You can check also the devices' models to learn about physics parameters too.

-- The 2nd step is to do basic MOSFET simulations NMOS and PMOS (with different channel length to get an intuition about how your devices are performing -- for example, there are tech files that PMOS devices are very bad compared to NMOS devices (very low mobility for example))

(Note: If you are going to fabrication you should also check with the broker or foundry that you will send your GDS files to so that you can learn about the constraints about the tech file ( some features are available with extra charges - also rules may change depending on the fabrication even for the same tech file depending on the run-type you are applying for - for example, a mini-ASIC run where you will share a wafer with other customers)

 

[reza147]

Hello
There are several things to consider when choosing a transistor.
The current that the transistor must pass.
The voltage at which the transistor must operate.
Transistor operating power.
Transistor type, appearance and dimensions.
Transistor inventory in your market.

You see, transistor BJT is cheaper than FET, but it has more power losses. FET transistor is more sensitive to noise! And there is a possibility of more burns.

Regarding the type of N or P: The type of N is more varied due to its easier construction and higher quality, and also due to its function, more circuits can be set up with it.

It is better to decide first whether you want N or P. Then consider some of the transistors available, and choose the best one.

Specify your data by writing down the requirements of your circuit, such as voltage / current / power / resistance, and the shape of the transistor, then select the best transistors by studying the datasheet. You can also see the characteristics of transistors in the comparison section of some store sites.

 

[KlausST]

Hi,

@reza:
Forum section, as well as headline tells "IC design".

Klaus