|Autors: Pandiev - IMP., Kovacheva - MGK.|
Title: VHDL-AMS Description of Digitally Programmable Gain Amplifiers through SPI
Keywords: Mixed-signal circuits, Programmable gain amplifiers, SPI, Be
Abstract: In this paper a behavioural VHDL-AMS models for digitally programmable gain amplifiers (PGAs) are presented. For creating the models, simplification and build-up techniques known from macromodelling of operational amplifiers have been adapted. The models accurately reflect input impedance, trans¬fer function (amplifier gain in binary steps versus controlling digital code through SPI), small-signal frequency response, large-signal pulse response, output characteristic (voltage and current limitations) and output resistance. Model parameters are extrac¬ted for the one channel PGA MCP6S21 and the two channels PGA MCP6S22 from Microchip. The behaviours of the equivalent circuits are created following their structures and operation principle. The modelling of the PGA behaviour is implemented and confirms to the format of the simulation program System Vision 5.5 (from Mentor Graphics). The simulation results show accurate agreement with the theoretical predictions.
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