# Two very basic question for circuit analysis

1. ## Two very basic question for circuit analysis

1. Difference between qualitative and quantitive analysis? If we want to perform these for any electronics circuit

What i know is in qualitative, observe data is not measured and in quantitive analysis observed data is measured.

2. Difference between small signal and large signal analysis (example- for MOS)?

What i know is small signal analysis is done only for "Change" parameter in circuit when input is nregelegile compare to dc parameter. Large signal analysis is like dc analysis (not all the time but most of the time) and we can apply KVL to calculate things.

I need more clarification on these two.

-Rahul

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2. ## Re: Two very basic question for circuit analysis

Originally Posted by Rahul Sharma
1. Difference between qualitative and quantitive analysis? If we want to perform these for any electronics circuit
qualitative: data are not calculated nor simulated nor measured; they are estimated - at best; quantitative analysis: data are calculated, simulated or measured.

Originally Posted by Rahul Sharma
2. Difference between small signal and large signal analysis (example- for MOS)?
Small signal analysis: fixed operation point, small modulation compared to DC operation points, i.e. e.g. microVolts at inputs, milliVolts at outputs. All required parameters (impedance, slew rate, gain, fT) are calculated, simulated or measured under assumption that DC operation points are stable. By analysis this is done in ac simulation: even if you sometimes get output voltages of Volts, kiloVolts, or even MegaVolts, this is still calculated under the assumption that DC operation points are unchanged, i.e. all impedances are linearized around their fixed operation point.

Large signal analysis: full modulation (sometimes up to output clipping). No fixed operation points anymore, i.e. the operation points move - while following the modulation - around their DC operation points, which so aren't stable any more. Means: no fixed impedances, i.e. all parameters can (and mostly will) change during the modulation; calculated or simulated parameter values result in mean values - at the best. Used for oscillators, or full modulation of amplifier circuits, their distortion, SFDR, 3rd order intermodulation distortion (IMD) and intercept point (IP3) calculation, analysis, or measurement.

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