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What is meant by drive strength?
drive strength capacitance In CMOS circuits the drive strength is the Current Capability of the device i.e. Ids. Ids can be increased by incresing the W/L ratio. It is with this current the present state can drive the next stage i.e. charge the next stage capacitance.
Why do you need drive strength?
Drive strength lets you accomodate heavier or lighter loads. As you increase the load (which at high-speed digital switching speeds is mostly capacitive), you need to be able to source enough current fast enough to charge or discharge the load capacitance.
What is fanout ratio?
A fan-out ratio is the relationship in quantity between a single port on a storage device and the number of servers that are attached to it. It is important to know the fan-out ratio in a storage area network (SAN ) design so that each server gets optimal access to storage resources.
How does drive strength affect the fanout of a cell?
Greater the drive strength, higher current can be drawn from the supply and the output capacitors can be charged quickly, if drive strength is low, then the current is less and the output capacitance takes time to charge/discharge. Hence the fanout of a cell is usually kept low to avoid driving problems.
What does drive strength of a device mean?
Drive strength is the current capability of the device, which is capable to drive the fan outs/output loads. The drive strength of the devices which is nothing but current carrying capacity can be increased by reducing the ON Resistance and Vice Versa. Thus ON resistance can be varied by varying two parameters of the devices
What does drive strength in STD cells mean?
Drive strength is the capacity of a cell to drive a value to the cell connected to its output. Different sizes of std cells have different capacitance, smaller cells have small capacitance and vice versa. Its easier to drive a small cell than a large one.
What is meant by drive strength in a CMOS circuit?
You can look at the schematic and see that gates with 2X drive strengths have approximately twice the widths on output pull up/pull down trasistors as comapred to the same gate with 1X drive strength. Similarly definitions for 3X, 4X etc.