Transistor load and saturation problem

In summary, the circuit in question involves determining the value of the resistor, R, for a current of 0.5 A to flow through the load, finding the maximum value of the load resistor, and calculating the value of VB that will put the transistor into saturation if the load resistor is 10Ω. The equations used are IC ≈ IE = VE/RE, IC ≈ (VB-0.6V)/RE, and ICRL+VCE+VE=Vcc. The resistor value for a current of 0.5 A is found to be 5.2Ω, and the maximum load resistor value is determined to be 27.8Ω. The VB value for saturation is found
  • #1
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Homework Statement


consider the following circuit:
attachment.php?attachmentid=58540&stc=1&d=1367880937.jpg


a) Determine the value of the resistor, R so that a current of 0.5 A flows through the load.
b) What is the maximum value of th load resistor?
c) If the load resistor is 10Ω, what value of VB will put the transistor into saturation?

Homework Equations



IC ≈ IE = VE/RE

IC ≈ (VB-0.6V)/RE

ICRL+VCE+VE=Vcc

The Attempt at a Solution


a) 0.5 ≈ (3.2 - 0.6)/RE
RE = 5.2Ω

b) (I am guessing that the VCE is 0.6 V here but I am not sure)
0.5RL+0.6+0.5 = 15
RL = 27.8Ω

c) From what I can tell, the transistor is an NPN and in that case, in order to saturate it, the base voltage must be greater than the collector or emitters'.

VC=ICRC
VC=(0.5)(27.8)=13.9V

VE=IERE
VE=(0.5)(5.2)=2.6V

So in order to be greater than both the VB must be greater than 13.9V

Parts b and c I was not so sure about, thanks for any input.
(Sorry that the image is not nicely sized, I'm not sure how to fix it.)
 

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  • #2
a) is right.
b): where does the 0.5 come from? Fact: Ve + Vce + iRL = 15. You have Ve already (= iR). You can increase the load R until saturation, Vc = Vb. You know Vb so go for it.

c) Yes, saturation is when Vb = Vc. So let the load resistor = 10 ohms; then how high must Vb be to get Vc = Vb?
 

Related to Transistor load and saturation problem

1. What is a transistor load?

A transistor load is a component in a circuit that is connected to the output of a transistor. It is used to provide a stable output voltage and current, and can be either resistive or reactive.

2. How does a transistor load affect the operation of a transistor?

A transistor load affects the operation of a transistor by controlling the flow of current through the transistor. If the load is too high, it can cause the transistor to saturate, which can lead to distortion or damage to the transistor.

3. What is the saturation problem in transistors?

The saturation problem in transistors occurs when the transistor is unable to amplify the input signal due to being fully turned on. This can result in distortion or clipping of the output signal.

4. How can the transistor saturation problem be avoided?

The transistor saturation problem can be avoided by carefully selecting the transistor load to ensure it does not exceed the maximum current and voltage ratings of the transistor. Using multiple transistors in parallel can also help distribute the load and prevent saturation.

5. What are some common causes of transistor saturation?

Some common causes of transistor saturation include using a load with a resistance that is too low, applying a high input voltage, or using a transistor with a low current and voltage rating. Poor circuit design and layout can also contribute to transistor saturation.

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