Electronic – meant by dc drop

circuit analysissemiconductorstransistors

What is the exact meaning of the term dc drop in transistors?
In solving the problem in the image given below , I was asked to find the dc drop across the collector resistance as shown in circuit so I thought it may be voltage drop but it is not as can be seen the solution(pdf link in comments)

  ${Any\ Help\ Is\ Greatly\ Appreciated}$

[circuit
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Best Answer

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Redrawn circuit with higher voltages at top.

It should be easier to understand if we redraw in a more conventional manner with higher voltages at the top, etc.

  • Voltage at A will be equal to Vcc, the supply voltage.
  • The voltage at B will depend on how much current is able to flow through Q1. This, in turn, will depend on how "turned-on" Q1 is.
  • The voltage drop is simply \$V_A- V_B\$.

A quick example:

  • Vcc = 12 V.
  • Rc = 1 kΩ.
  • Ic (the current through Rc and Q1) = 5 mA.

From Ohm's Law, \$ V = IR \$ we get the voltage drop across Rc as \$ V = 0.005 \cdot 1000 = 5~V \$.

We can, using this result, calculate \$ V_B = 12 - 5 = 7~V \$.