ABSTRACT
This chapter discusses the documents small-signal performance equations, general operating characteristics, and engineering design guidelines for the several most commonly used global feedback circuits. Four basic types of single-loop feedback amplifiers are available: the series-shunt, shunt-series, shuntshunt, and series-series architectures. Only two types of global dual-loop feedback architectures are used: the series-series/shunt-shunt feedback amplifier and the series-shunt/shunt-series feedback amplifier. The shunt-shunt nature of the subject amplifier suggests the propriety of y-parameter modeling of the feedback network. The uncompensated closed loop is therefore predisposed to unacceptable underdamping, thereby making compensation via an introduced feedback zero difficult. In general, negligible feed-forward through the feedback subcircuit is advantageous, particularly in high-frequency signal-processing applications. However, similar to the shunt-shunt triple, frequency compensation via an introduced feedback zero is difficult unless design care is exercised to realize a dominant pole open-loop response. When the shunt-series component of the feedback amplifier is activated, the dual-loop configuration functions as a current amplifier.
