... Tears¹

Well, maybe with only a few tears

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... it!²

This points to a critical difference between science and engineering. Scientists want to understand the universe. Engineers want to build things. Scientists therefore want models that give insightful descriptions, while engineers want models that enable them to build useful artifacts.

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... down''.³

Not everyone uses these convention. Another common convention for reference currents is to have all three directions point towards the device. These conventions are the sorts of things that EE professors have violent arguments about, which says more about the personalities of EE professors than it says about transistors.

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... one.⁴

If it is intended to be an amplifier, it will clip the waveform when it enters the cutoff region, producing distortion.

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... transistors⁵

In contrast to small-signal transistors, power transistors may have $\beta$ around 25. Transistors inside an integrated circuit like an op-amp might have $\beta$ values in the thousands.

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... values.⁶

The $q/kT=38$ is for room temperature. $I_0$ scales with the size of the transistor.

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... 6.002x.⁷

The are methods for analyzing arbitrary circuits. These methods, which involve complex numeric and symbolic computations with sophisticated transistor models, are used mainly to verify designs. In 6.002x we concentrate on hand calculation of simple circuits using simple models, which provides a foundation for design and can be a good source of insight for the circuit designer.

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