Sallen-Key Differential Filter Amplifier

A combination of three operational amplifiers is used in the shown analog circuit to implement a differential lowpass filter amplifier with an overall gain that is controllable by the ratio of two resistor and also a potentiometer or variable resistor in the circuit. A combination of KCL, superposition, virtual short, inverting amplifier and non-inverting amplifier op amp topology is used to analyze the circuit and find the overall voltage transfer function which has a second order denominator due to two capacitors in the Sallen-Key VCVS filter topology. Bode magnitude plot (magnitude frequency response) of the filter, Poles of the system and overall gain are discussed as well.

[@wafikiri_]

Thank you for the video.

[@STEMprof]

Thank you for watching. Glad that you liked this Sallen Key differential amplifier circuit.

[@STEMprof]

Thanks for watching. Here are more Sallen-Key Filter Design examples using Op Amps:
Sallen-Key Filter Design ruclips.net/video/yHBsKTAn3VA/видео.html
Sallen-Key Analog Filter Design Tutorial ruclips.net/video/KwUnQXbk7gM/видео.html
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ruclips.net/video/HeZRtnRXpEI/видео.html presents a circuit with op amps and feedback loops to design an analog computer that solves a second order differential equation.
For more analog signal processing examples see: ruclips.net/p/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt
I hope these Analog High-pass, Low-pass and Band-pass filter design and analysis examples are interesting and helpful.

[@voice4voicelessKrzysiek]

You lost me at the end but I enjoyed the process anyway. Thanks.

[@STEMprof]

Thanks for watching and sharing your feedback. Glad that you enjoyed the process and analysis of the circuit. At the end of this video I am conducting S domain pole-zero and Transfer Function analysis. Here are few more Sallen-Key Filter Design examples that might help:
Sallen-Key Filter Design ruclips.net/video/yHBsKTAn3VA/видео.html
Sallen-Key Transfer Function ruclips.net/video/LYARYxwUJgc/видео.html

[@STEMprof]

Thanks again for watching. I hope the new video is helpful: How to find Bode Plot, Freq Response, Transfer Function of Analog Filters ruclips.net/video/vZFkPeDa1H8/видео.html . I hope you find it interesting as well. :)

[@wafikiri_]

I wouldn't know how to choose a suitable k factor. The RC time product is easy to choose if frequencies are given, though.

[@STEMprof]

Well said about the RC time constant that is defined by the choice of cutoff frequency of the filter. A good choice for K=2 which translates to using same value for the two last resistors at the out put of the circuit. Otherwise the choice of K also affects the position of poles (roots of denominator of transfer function). I hope this is helpful.

[@wafikiri_]

@@STEMprof I'm trying to design a pipelined variant of the processor I designed, and, at some point, I devised a way to evaluate contention on resources such as the Arithmetic Logic Unit or memory access. Suddenly I thought of using digital-to-analog conversion so as to quickly evaluate contention and execute the instruction step with the highest value without resourcing to cumbersome, multiple, slow binary addition and comparation: a few op-amps and resistors would do. Like a set of neurons. Nothing similar to filters or PSUs, but in this case I think op-amps would do a wonderful job.