Памятка: Vcc, Vdd

VCC – Voltage Collector Collector. Positive supply voltage.
VDD – Voltage Drain Drain. Positive supply voltage.
VEE – Voltage Emitter Emitter. Negative supply, ground.
VSS – Voltage Source Source. Negative supply, ground.

VCC – For TTL circuitry, this is the +5 volts which sits on the collector of the bi-polar transistor output circuit.
VDD – For CMOS circuitry (like the PIC) this is the +5 (or +3) voltage that sits on the ‘drain’ of a MOS-FET transistor output circuit.
VEE – For TTL circuitry, this is the GND which sits on the emitter of a bi-polar transistor output circuit.
VSS – For CMOS circuitry, this is the GND that sits on the ‘source’ of a MOS-FET transistor output circuit.