BJT biasing revisited

Abstract

The familiar four resistor circuit for biasing a Bipolar Junction Transistor (BJT) is generalised through simple reasoning, and transformed to yield a different topology. Three alternative four resistor circuits are derived as special cases of the transformed generalised circuit, which do not appear to have been widely known in the literature. A detailed and careful analysis reveals that the bias stability parameters of all the alternative circuits are comparable to those of the conventional circuit. An illustrative example is included for demonstrating this fact.