Circuit Calculator is an offline interactive professional electronics design tool for engineers.
Convenience visibility and ability to find an optimal solution in minimum time.
120+ analog circuit topologies 50+ electronics calculators 20+ Application Notes Logic Solver.

You can try "Circuit Calculator Demo" before you buy:
https://play.google.com/store/apps/details?id=com.vdv.circuitcalculator.demo

This electronics design tool is designed by an engineer for engineers and is able to save you a lot of time!

* Amplifiers;
* Variable Gain Amplifiers;
* Drivers;
* Current Sources and Receivers;
* Lowpass Highpass Bandpass Bandstop Filters;
* Mathematical Operations;
* Power Circuits;
* Switching-Mode Power Supply Modules;
* Control Loop Compensation;
* Others Passive and Active Circuits;
* Reverse: calculation of circuit parameters at known values of its components if it is possible;
* Logic Solver from 2 to 6 inputs;
* Auxiliary electronics-specific tools;
* Application Notes;

You can use Filter Designer to design multistage active analog filters available in the Google Play Store.
https://play.google.com/store/apps/details?id=com.vdv.filterdesigner