What are the tolerances of five band resistors?
Most five band resistors are precision resistors with tolerances of either 1% or 2% while most of the four band resistors have tolerances of 5%, 10% and 20%. The colour code used to denote the tolerance rating of a resistor is given as: Brown = 1%, Red = 2%, Gold = 5%, Silver = 10 %.
How to calculate the resistance of a transistor?
Now, let’s calculate the correct resistance value for resistor Rc. Let Vcc = 5V, V (LED) = 1.9V, V CE (sat) = .1V, and I C (MAX) = 15 mA. The answer is: The calculation shows that we need a 200 ohm resistor for Rc in order to limit the current through the LED to a safe 15 mA.
Is it possible to use an arbitrarily high resistor?
Yes, to a certain extent. You can’t use an arbitrarily high resistor– giving you an arbitrarily small amount of emitter-base current through the PNP transistor –because the PNP transistor has finite gain. That gain is in the neighborhood of 100, if we used (for example) a 2N3906 transistor.
How is an emitter resistor used in a transistor?
The simple solution, shown in Fig. 4.19B, is to add a base–emitter resistor to any transistor, which is threatened by leakage currents. The resistor is sized to divert only a modest proportion of the base current (typically one-tenth) when the transistor is being driven on.
Most five band resistors are precision resistors with tolerances of either 1% or 2% while most of the four band resistors have tolerances of 5%, 10% and 20%. The colour code used to denote the tolerance rating of a resistor is given as: Brown = 1%, Red = 2%, Gold = 5%, Silver = 10 %.
How is the resistor of a transistor sized?
The resistor is sized to divert only a modest proportion of the base current (typically one-tenth) when the transistor is being driven on. In the example above, assume that the base current of TR2 is set to 1 mA in the on-state; then taking VBE = 0.6 V at this current, RL is 0.6 V/0.1 mA = 6 kΩ.
Yes, to a certain extent. You can’t use an arbitrarily high resistor– giving you an arbitrarily small amount of emitter-base current through the PNP transistor –because the PNP transistor has finite gain. That gain is in the neighborhood of 100, if we used (for example) a 2N3906 transistor.
How is the current limited in a transistor?
As the transistor acts as a closed switch, the current is limited only by the resistor. This is our first point of the line: If Ic = 0 no current is flowing. This means that there’s no voltage drop in the resistor (V = I·R) and all the voltage drops in the transistor (Vce = Vcc).