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# Transistor sizing of TCAM CELL

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#### nagakarthik

##### Newbie level 2
How i should proceed with the transistor sizing ? I am using 0.35um technology. Length and Width of the transistors are 500nm and 1.2um respectively. i have completed the designing of the TCAM CELL but i am unable to adjust the transistors. Can you please give the info in detail..

To check the cell performance (verification) you have to simulate it, e.g. with HSpice. You need a netlist and model files and .extract statements for the relevant performances.
To size the transistors, there are basically two approaches:

1) symbolically approximative: you start with simplified transistor model equations and develop equations that approximate the relevant circuit performance metrics as functions of the device geometries, then solve for the geometries. Effort, difficulty and accuracy depend on the circuit and model. It's often easy for AC and DC, but not for TRAN specs. For large memories you also have to take local Vt variation into account.

2) numerically: you run a circuit optimization program that runs HSpice in a loop and tunes the circuit for you, to fulfill the specs and reduce process sensitivity.

The first method works well for small low frequency analog designs and is taught in analog design classes and student text books extensively, to improve student's circuit understanding. The second method is the one that works for advanced node RF designs, post-layout tuning, high-speed I/O, full-custom digital, standard cells, large complex analog blocks. It is usually not taught at university.

Thank you for your reply..according to your suggestion first approach is Ok and for second approach i am not using HSpice am using cadence software. Can you tell me how to use in cadence.

Thank you for your reply..according to your suggestion first approach is Ok and for second approach i am not using HSpice am using cadence software. Can you tell me how to use in cadence.

HSpice was just an example, because it's the most popular for this kind of cells, but it works just the same with Spectre, with the difference that you don't define .measure statements but ADE output expressions with the waveform calculator. If you are interested in more details, you can request product sheets at info@muneda.com .

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