Chapter 4 - Bipolar Transistor Models

Abstract

This chapter builds on the device model work discussed in the previous chapter, and models for the ideal bipolar transistor are derived. Rather than deriving the full transistor equations, we will rely on results from the ideal diode and “talk through” intuitively how the bipolar transistor works. The NPN transistor is considered, but results obtained are germane to analysis of the PNP transistor as well. Most of this discussion will focus on operation of the bipolar transistor in the “forward-active” region, the region of operation where the transistor can be used as an amplifier. In a later chapter, we will extensively discuss operation of the bipolar transistor in the saturation and cutoff regions.