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!

* 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
+ Share circuit with friends
+ Themes (Dark, Light, Ocean, Solarized)
+ PNG, JPG, PDF circuit export
+ Export workspace
+ Video tutorials about electronics

Components:
+ DC, AC, Square, Trinagle, Sawtooth, Pulse, Noise voltage source
+ Current source
+ Resistor
+ Potentiometer
+ Capacitor
+ Polarized 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, NXOR, Inverter)
+ Voltmeter
+ Ammeter
+ Fuse
+ Photoresistor (uses phone light sensor)
+ Analog-to-digital converter (ADC)
+ Accelerometer (uses phone accelerometer sensor)
+ FM source
+ Logic Input
+ Memristor
+ Logic output
+ Probe
+ Voltage rail

Analog Pack:
+ Tunnel diode
+ Varactor
+ NTC Thermistor
+ Center tapped transformer
+ Schmitt trigger
+ Schmitt trigger (inverting)
+ Solar cell
+ TRIAC
+ DIAC
+ Thyristor
+ Triode
+ Darlington NPN
+ Darlington PNP
+ Analog SPST
+ Analog SPDT
Digital Pack:
+ Adder
+ Counter
+ Latch
+ PISO Register
+ SIPO Register
+ Seven segment decoder
+ Sequence generator
+ D Flip-flop
+ T Flip-flop
+ JK Flip-flop
+ Multiplexer
+ Demultiplexer
+ Voltage controlled current source (VCCS)
+ Voltage controlled voltage source (VCVS)
+ Current controlled current source (CCCS)
+ Current controlled voltage source (CCVS)
+ Optocoupler

Misc Pack:
+ Wobbulator
+ AM Source
+ SPDT Switch
+ Digital to analog converter (DAC)
+ Antenna
+ Spark gap
+ LED Bar
+ 7 segment LED
+ RGB LED
+ Ohmmeter
+ Audio input
+ Microphone
+ Device battery
+ DC Motor
+ 14 segment LED
+ Diode bridge
+ Crystal
+ Voltage regulators (78xx family)
+ TL431
+ Buzzer
+ Frequency meter

JavaScrip Pack:
+ Write code
+ JavaScript interpreter (ES2020 class)
+ Access to IC inputs in code
+ Access to IC outputs in code
+ Four custom ICs

7400 TTL Pack:
+ 7404 - hex inverter
+ 7410 - triple 3-input NAND Gate
+ 7414 - hex Schmitt-trigger inverter
+ 7432 - quadruple 2-input OR gate
+ 7440 - dual 4-input NAND buffer
+ 7485 - 4-bit magnitude comparator
+ 7493 - binary counter
+ 744075 - triple 3-input OR gate
+ 741G32 - single 2-input OR gate
+ 741G86 - single 2-input XOR gate

4000 CMOS Pack:
+ 4000 - dual 3-input NOR gate and inverter.
+ 4001 - quad 2-input NOR gate.
+ 4002 - dual 4-input NOR gate.
+ 4011 - quad 2-input NAND gate.
+ 4016 - quad bilateral switch.
+ 4017 - 5-stage Johnson decade counter.
+ 4023 - triple 3-input NAND gate.
+ 4025 - triple 3-input NOR gate.
+ 4081 - quad 2-input AND gate.
+ 4511 - BCD to 7-segment decoder.

Sensors pack:
+ Pressure
+ Gyroscope
+ Light
+ Magnetic field
+ Proximity
+ Temperature
+ Humidity