Are you looking for tools like Multisim, SPICE, LTspice, Proteus or Altium? That's great! PROTO is an real time electronic circuit simulator which means you are able to setup a circuit with various components and simulate behaviour of the electronic circuit.
During simulation you can check voltages, currents and many other variables. Check signals on multichannel oscilioscope and tune your circuit in real time! You can also use PROTO as logic circuit simulator and perform digital electronic analysis!

* PLEASE KEEP IN MIND THAT THIS APP IS IN ALPHA STAGE :) *
* You can report an issue or make component request at https://github.com/Proto-App/Proto-Android/issues *

Features:
+ Animations of voltage values and current flows
+ Adjusts circuit parameters (like voltage, current and other)
+ Four-channel oscilloscope
+ Single play/pause button to control simulation
+ Copy electronic components
+ Learn about electronic circuits by examples in app

Components:
+ DC, AC, Square, Trinagle, Sawtooth, Pulse, Noise voltage source
+ Current source
+ Resistor
+ Potentiometer
+ Capacitor
+ Inductor
+ Transformer
+ Diode (rectifying diode, LED, Zener, Schottky)
+ Transistor (NPN, PNP, N and P channel Mosfet)
+ Switches (SPST, Relay)
+ Bulb
+ Operational amplifier
+ Timer 555 (NE555)
+ Digital Gates (AND, NAND, OR, XOR, NOR, Inverter)
+ Voltmeter
+ Ammeter
+ Fuse
+ Photoresistor (uses phone light sensor)
+ Analog-to-digital converter (ADC)
+ Accelerometer (uses phone accelerometer sensor)
+ FM source
+ Logic Input
+ Memristor