Fig 5.
Partitioning of a circuit to allow analysis by using the feedback formalism presented here. For a noise source at any location within the circuit, the transfer functions A(f) and β(f) are defined. A(f) is the transfer function from the noise source location to the output (i.e., location where noise behavior is to be calculated) and β(f) is the transfer function from this output back to the noise source location.
