In many circuits, Vss/Vee is the same as the ground node, in which case it may or may not ever be noted as being Vss or Vee. The strict meaning of these has been lost among a growing number of people, and hence you will often see Vcc used as the positive supply in CMOS circuits and see Vdd in BJT circuits. The same remarks regarding polarity apply here. A quick glance at the schematic will tell you if this is the case or not.įor MOSFET circuits, the three common suppies are Vdd, Vss, and Vgg for the drain, sourse and gate supply voltages. This is commonly, but not universally, the case even if the only transistors in the circuit are PNP transistors. One fine point is that, by general convention, Vcc and Vee are associated with the collector and emitter sides of an NPN transistor.
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The Vbb is sometimes an actual supply, but more often it is the thevenin equivalent voltage associated with the base bias network. The letter would generally have some relevance to what the purpose of the supply was.įor BJT circuits, the three common supplies are Vcc, Vee, and Vbb for the collector, emitter, and base voltage supplies. Since any voltage with a repeated subscript will be 0V, the convention was adopted that a repeated subscript would indicate that the voltage was referring to a supply voltage, usually a DC supply. So, at this point, what would Vcc or Vee (or any other voltage with a repeated double subscript) be? So in an expression, I can combine to voltages provided the first subscript on one of them is the same as the second subscript on the other by dropping the common subscript and keeping the other two in their same position. Vac = (Va - Vb) + (Vb - Vc) = Va + (-Vb + Vb) - Vc = Va - Vc Well, I can use the subscipts to tell me that
![char math arduino char math arduino](http://c.51hei.com/d/forum/201712/29/230945yzph6jzawpbdr744.jpg)
This notation is actually quite useful because it allows you to figure out an unknown voltage step by step.įor instance, let's say that I want to know Vac but I only know Vab and Vbc. If you have Vab or other voltages with two subscripts, then what is meant is the voltage of the first node with respect to the second node or
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You are free to pick any node you want as your reference node, but usually one or two nodes are the most reasonable candidates.
![char math arduino char math arduino](http://c.51hei.com/d/forum/201703/15/231148uh2du9nv2t8n8fnv.png)
That reference node is "ground" or "common" and is usually just indicated as "GND" or something similar. If you have Va, Vb, or other voltages with a single subscript, then what is meant is the voltage of that node with respect to some reference node. Click to expand.They are derived from a more general naming convention.