Leapfrog Filters By continuing the concepts of operational simulation, higher order filters can be built Each inductor requires an inverting integrator (1 op- amp), each capacitor requires a non-inverting integrator (2 op-amps) Op-amps required = 3N/2 Complex circuits can be simulated using similar principles Scale factors for all variables can be adjusted arbitrarily By doing this, the output voltage range for each op- amp can be adjusted to maximise the dynamic range of the filter
Comparison of Active Filter Designs Synthesis by Sections Low op-amp count – N/2 Noise/output voltage range trade off Sallen & Key sensitivity Component Simulation Robust despite component tolerances Higher op-amp count – N Easier to realise transmission zeros Dynamic range limitation Operational Synthesis Robust again Even higher op-amp count – 3N/2 Op-amp output ranges can be individually optimised.
Revision What should you be expected to do in a typical exam question ? Understanding of basic principles. Ability to perform simple circuit analysis and/or design. Applying skills to unfamiliar problems.
Power Amplifiers Basic Principles Operating modes of amplifiers Power dissipation and thermal effects Design/Analysis Class A, B, AB amplifiers Use of multiple transistor units (Darlington) Associated circuits (current mirror, V BE multiplier)
Low Noise Amplifiers Basic Principles Noise figure and noise temperature definitions Sources of noise Equivalent circuits Design/Analysis Noise figure of a common-emitter amplifier
High Frequency Amplifiers Basic Principles Frequency response calculations Internal junction capacitances of a BJT The Miller effect Design/Analysis Frequency responses of A common-emitter amplifier A cascode amplifier
Active Filters Basic Principles Types of filter and differences between them Transfer functions, poles and zeros Design/Analysis Synthesis by sections, first and second order Sallen and Key sections Component simulation for Grounded inductors Floating inductors Grounded FDNRs Operational Simulation: Ring of Three