Simple circuit with dependent source interpretation
Because real circuits cannot contain any current sources, we - at first - can replace the current source Is and the shunt resistor R1 by a corresponding (equivalent) voltage source V3 and a series source resistor Ri. Now - there are two resistors in series (Ri - R2) and the common node labelled as Va is identical to the base node (because the corresponding node voltage Vx acts as an input to the controlled current source).
Therefore, the resistor R2 connects the collector with the base which means: negative feedback.







simulate this circuit &ndash; Schematic created using CircuitLab