# : (In electronics ) differences between VCC, VDD, VSS, VEE, and VPP

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In electronic circuits, there are different symbols for voltage: VCC, VDD, VSS, VEE, and VPP? What is the difference between them?

In: 4

Generally if you get all 5 its because someone had too many power pins

In general, Vss is tied to ground with Vcc and/or Vdd being the positive voltage (5V or 12V or similar)

Vee is significantly less common but is generally equivalent to Vss when used with BJT circuits, its tied to the Emitter of the BJTs rather than Vss being at the Source of the FETs, both are generally the lowest voltage being applied to that portion of the chip

Certain chips will take both a Vcc and a Vdd, maybe it has two separate power circuits inside itself running at different voltages and you feed Vcc +3.3V and Vdd +5V for some logic level operations.

In general, consult your data sheet for what each random acronym they’re using means to them because some companies use slightly different terms and definitions.

A voltage is a potential difference between two points, so Vab is the voltage at a referenced to b. With those same-letter voltages, they are generally power supply (as opposed to signalling) voltages relative to an implied ground rail.

Vcc is the voltage at the ‘collector’ end of a NPN bipolar transistor, used with old style TTL devices which used such in their output stages. It was almost always 5v.

Vdd is the corresponding voltage at the drain end of an N-channel Mosfet, for ICs which used such in their output stages.

Vss is the corresponding voltage at the source end of such transistors. It is almost always taken as meaning the 0v rail and is often used even when the supply is denoted as Vcc (bipolar).

Vee is a bias voltage applied to ECL ics, where the ’emitter parts’ need to be brought to a voltage lower than Vss.

Vpp is the programming voltage initially used on old EPROMs and the like. It was anywhere from 12v to about 28v, depending on technology of the storage array. It’s still used in some flash devices these days and sometimes just as a ‘go into programming mode’ signal, rather than be a high current power supply for changing the internal electron energies in an old EPRON.