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Physical Design Methodology Engineer at Texas Instruments

  Hello Dear Readers, Texas Instruments Bangalore has a vacancy for the Physical Design Engineer role. We need an Physical Design Methodology Engineer to join our ATD team. The candidate should have a strong background in back-end design of ASIC/SoC chips. The ideal candidate will have a bachelor’s or master’s degree in Electrical Engineering or a related field. Requirements: 1 - 2 Years of experience in physical design Bachelor’s or master’s degree in Electrical/Electronics Engineering or a related field Strong understanding of physical design principles Must know the basics of floorplan, placement, CTS, routing, ECO, Physical Verification Proficiency in back-end design tools, such as Cadence Genus/Innovus/Tempus/Voltus Excellent problem-solving skills and attention to detail Effective communication and collaboration skills Responsibilities: Synthesis to GDSII Perform full Physical design flow and its verification Work closely with Digital Design and DFT engineers Ensure...
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CMOS Inverter-Layout Design And It functional Verification SPICE Simulation

 Hello Dear Readers,

Today, I will explain how to design a Layout in the MAGIC layout tool and how to perform SPICE simulation.

CMOS inverters (Complementary NMOSFET Inverters) are some of the most widely used and adaptable MOSFET inverters used in chip design. They operate with very little power loss and at relatively high speed. Furthermore, the CMOS inverter has good logic buffer characteristics, in that, its noise margins in both low and high states are large.

A CMOS inverter containing a PMOS and an NMOS transistor connected at the drain and gate terminals, a supply voltage VDD at the PMOS source terminal, and a ground connection at the NMOS source terminal Vin is connected to the gate terminals, and Vout is connected to the drain terminals As shown in Fig.1 is a circuit-level symbol but in the layout-wise internal structure of CMOS is consisted of common P-Type Substrate for building NMOS and N-Well implanted for building PMOS as shown in Fig.2.

                       Fig.1 CMOS Inverter

          Fig.2 CMOS Inverter Internal Structure

So Let's Start the Layout Once You Open the Magic Layout tool Screen is coming as shown in Fig.3. Go to the Window menu and click on "Grid on". So one grid is a square with one lambda by one lambda. So placing layers in magic we need to left-click hold it and right-click where we want to end the shape of the layer. So first I have to build N-well and p-type diffusion overlap as shown in Fig.4 all sizes are optimized by lambda-based design rules.

Fig.3 Magic Layout initial screen

Fig.4 N-well And p-type diffusion overlap

After that now we want to draw a polysilicon layer to build the gate terminal of PMOS. After that metal-1 and substrate contacts layer formed to build complete PMOS as shown in Fig.5. Similarly, we build NMOS and shorted Polysilicon of PMOS and NMOS together to the formed input terminal of the Inverter and shorted the drain layer to the formed output terminal as shown in Fig.6. After that we have to provide labels of VDD, gnd, in, and out as shown in the final layout.  

Fig.5 PMOS

Fig.6 CMOS Inverter final layout

So after the final layout save the layout go to the command line screen of the magic and type first "extract all" and then "ext2spice" as shown in Fig.7. Now go to path in which layout is saved so we found the .spice format file and .mag format file. So copy the .spice file and make a new directory on which paste it and then go to the PTM model and copy the entire web page and make the text file in the same directory on which the spice file was saved. Now open spice file and do some changes such as include model file, apply the supply voltage and input pulse signal for functional verification as shown in Fig.8.


Fig.7 Extract Layout

Fig.8 Updated SPICE file

Now open the terminal from this directory and open Ngspice with spice file as shown in Fig.9 and type command "run" first and then type "plot in out". The simulational waveform is shown in Fig.10.
Spoken Tutorial found Here.


Fig.9 Ngspice simaltion
 
Fig.10 Simulation Waveform of CMOS Inverter



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Comments

  1. Anonymous24 August 2021 at 06:58

    Wow first time all doubts regarding Magic plus Ngspice is solved.thanks for your effort

    ReplyDelete
  2. Anonymous24 August 2021 at 08:34

    One of the blog in which I found this much easy explanation and project wise learning. Bro keep it up and never stop this work.

    ReplyDelete
  3. Anonymous24 August 2021 at 09:24

    Fantastic learning based post.

    ReplyDelete
  4. Anonymous30 August 2021 at 02:09

    You are a next level motivation person. Really in india I never find other blog such user friendly.

    ReplyDelete
  5. Anonymous10 September 2021 at 19:08

    You are really slow learner, I really like your content accuracy specifically verilog code is always bugs free. So best wish and keep it up

    ReplyDelete
  6. John18 September 2021 at 23:59

    Amazing! Accurate and very well explained.

    ReplyDelete
  7. Anonymous26 September 2021 at 09:09

    This comment has been removed by a blog administrator.

    ReplyDelete
  8. Anonymous15 January 2022 at 01:22

    Really helpful for beginners

    ReplyDelete
  9. Anonymous16 August 2022 at 21:28

    So simple and solved all the query regarding extraction and spice simulation. Thanks dear for your effort 😶😶😶😶

    ReplyDelete
  10. Anonymous8 November 2022 at 22:15

    One of the excellent post regarding layout verification through spice simulation. I read your post regularly and big fan of you 👍👍and I am a professor at IITH.

    ReplyDelete
    Replies
    1. ELECTRONICS AND COMMUNICATION HUBS9 November 2022 at 22:51

      It's my motivation thanks sir for your feedback and appreciation. I will do my best forever.

      Delete
  11. Anonymous5 December 2022 at 03:52

    One of superb article

    ReplyDelete
  12. Anonymous24 December 2022 at 10:25

    Superb post I really like the way of the contents and simpler explanation.

    ReplyDelete

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