Optimizing Power, Speed, and Size: Tips for CMOS Circuit Design"

[vead]

when designer design new circuit, they think what's the requirement

step I
1)power dissipation should be less
2)raise time and fall time should be less
3)propagation delay time should be less
4)size should be small as possible

step II

1) how can we reduce power dissipation in cmos circuit?

- we have to decrease voltage or current in circuit
- we have to decrease resistance in circuit

2) how can we reduce raise time and fall time?
-which parameter depend on raise and fall time

 

[Baluncore]

Do you want high speed or low power? You must select a compromise.

Use smallest possible geometry active elements to get less capacitance and less charge storage.

Clock the circuit as slowly as possible. Design so minimum outputs and inputs change each cycle.

Use the lowest possible supply voltage, but make sure there is no through current when both pull up and pull down outputs conduct.

 

[vead]

1) how can we reduce power dissipation in cmos circuit

 

[analogdesign]

Most digital designers don't have to worry much about things like rise/fall time and prop delay. They just make sure the process they are using is fast enough then they focus on the logical design (using a hardware description language).

Baluncore told you how to reduce power dissipation.

If you're actually designing custom CMOS layout (unlikely) then you reduce capacitance by making devices small and using high level metal for routing when possible. You reduce resistance by making wide wires (although this makes capacitance more... there is a compromise, as Baluncore said).

 

[alphy]

- we can reduce the parasitic capacitance in the circuit by using techniques such as minimizing the length of interconnects and using smaller transistors.
- the rise and fall time also depend on the load capacitance, so we can optimize the load capacitance by using smaller capacitors or using techniques such as parallel loading.
- the transistor sizing also plays a role in the rise and fall time, so we can optimize the sizing of the transistors to reduce the time.
- we can also use techniques such as pre-charging and buffering to reduce the rise and fall time.
- the technology used for the circuit also affects the rise and fall time, so using advanced technologies with smaller feature sizes can help in reducing the time.

3) how can we reduce propagation delay time?
- which parameter depend on propagation delay time

- similar to reducing rise and fall time, we can optimize the parasitic capacitance, load capacitance, and transistor sizing to reduce the propagation delay time.
- we can also use techniques such as pipelining and parallel processing to reduce the delay.
- the technology used also affects the propagation delay time, so using faster and more advanced technologies can help in reducing the delay.

4) how can we decrease the size of the circuit?
- which techniques can be used to reduce the size of the circuit

- we can use techniques such as layout optimization, where we carefully design the layout of the circuit to minimize the area.
- we can also use techniques such as transistor sizing and gate sizing to reduce the number of transistors and gates used in the circuit.
- using advanced technologies with smaller feature sizes can also help in reducing the size of the circuit.
- we can also use techniques such as folding and stacking to reduce the physical size of the circuit.
- optimizing the interconnects and using smaller components can also contribute to reducing the overall size of the circuit.

In conclusion, optimizing power, speed, and size in CMOS circuit design requires careful consideration of various parameters and techniques. By reducing power dissipation, rise and fall time, propagation delay time, and overall circuit size, we can achieve more efficient and high-performance circuits. This involves a combination of design techniques, technology choices, and careful layout optimization to meet the requirements of the circuit design.