Description
The basic principles of the operation of the four basic active elements, as described in Book 1, provide a good foundation for further study of electronic circuitry. Analog amplifiers constitute a major class of electronic circuitry and are a primary component in many applications. While it has been shown that electronic devices are basically non-linear, amplifiers typically operate within a region of incremental linearity. at is, a region where small variation in the input produces linearly amplified variation in the output. Analysis of such systems uses the principle of superposition: DC (or bias) conditions are separated from the AC (or variational) components of the input and output of an amplifier. The term ”small-signal analysis” refers the use of linear models. ”Large-signal analysis” implies operation near the transition between operational regions of an active device: such large-signal operation is typically non-linear and leads to distorted amplification. This book begins with a review of two-port analysis. is review provides a basis for modeling transistors: they are most commonly modeled as two-port networks for small-signal analysis.
At low frequencies the BJT is modeled by an h-parameter two-port and the FET as a modified hybrid- two-port. Simple amplifiers are approached by observing the previously observed region of operation that appeared between the two logic states of an inverter. All single-transistor amplifier configurations are analyzed and performance characteristics compared.
Multiple transistor amplifier circuitry is initially approached through cascading single transistor amplifiers using capacitive coupling. Only after the basic concepts are mastered, are the more complex circuits studied. Compound transistor configurations, such as the Darlington circuit, and direct-coupled amplifier stages are studied. As with single-transistor amplifiers, the previously observed linear region in ECL logic circuits leads to the study of emitter-coupled and sourcecoupled amplifiers. Common integrated circuit practices such as current source biasing and active loads are discussed.
Power amplifiers provide a good counterexample to the use of small-signal analysis. By necessity, the output of a power amplifier is not small and consequently may contain distorted components. Both harmonic and intermodulation distortion analysis techniques are introduced and compared. Amplifier conversion efficiency is discussed for class A, B, and AB power amplifiers. Thermal considerations are presented using simple heat transfer models and are related to power amplifier design criteria and limitations.
Feedback principles are introduced initially as a technique to stabilize amplifier gain, reduce distortion, and control impedance. e various configurations are introduced and analyzed