LED and a photo diode, used for isolation
LED and a signal diode, used for signal clamping
Transistor and LED, used for voltage amplification
Photo diode and Transistor, used for attenuation
Base width is increased
Doping of base is reduced
Power rating of the transistor is increased
Metal can packaging is used
Can be used to know whether two digital inputs are identical
Is a NOT followed by OR
Two OR gates followed by AND
Cannot be used for matching of two inputs
0xA5
0x56
0x74
0x66
7 flipflops
6 flipflops and one OR gate
5 flipflops and two AND gates
50 flipflops