Electronics Module Practice Exam: Solving Transistor Circuit Qs

[Myrddin]

Doing practice exam papers for electronics module, can someone explain to me how to go about this question?

http://img402.imageshack.us/i/electronicsquestions.jpg/

 

[berkeman]

Doing practice exam papers for electronics module, can someone explain to me how to go about this question?

http://img402.imageshack.us/i/electronicsquestions.jpg/

What do you know so far for how to bias a Common-Emitter (CE) BJT voltage amplification stage? Do you understand how to do the basic biasing, and are asking where the bandwidth portion of the question comes in? Or are you not familiar with BJT biasing at all?

If it's just the bandwidth part of the question, you have an input signal coupling capacitor, and the bias circuit & BJT together present an input impedance. What kind of filter does that form for input signals coupled to the input capacitor?

 

[Adjuster]

Have you been given information about the type of transistor used, or details of its characteristics, particularly its current gain and its base-emitter voltage?

Do you have any values for the DC conditions required, such as the collector current, the collector voltage (Vc in the diagram), or the emitter voltage?

The question page you have posted does not show any of this information, so unless you were given it elsewhere, you need to begin by choosing reasonable values. Can you do that?

 

[Myrddin]

Thats the whole question. I see there's a potential divider to find the values of resistance for Rb1 and Rb2, what i don't know know is what it means to "bias the amplifier". I am very unfamiliar with transistor circuits know only the very basics, the collector the base the emittor. Know that Vemitter = Vbase -0.6volts, and that its assumed that Ic = Ie as some rules of transisotrs.

From some notes iv got "Want Vcollector = 0.5 (Vin)" , is that what's needed to "bias the amplifier" ? if so i think can do it using those transistor rules and the fact there's a potential divider.

 

[DeeNos]

Sure, I'd be happy to help you with this question. First, let's take a look at the circuit diagram provided in the link. It shows a simple transistor circuit with a power supply, a resistor, and a transistor. The question asks for the voltage across the resistor, as well as the current flowing through the transistor.

To solve this question, we need to use Ohm's Law, which states that voltage (V) is equal to current (I) multiplied by resistance (R). In this case, we know the resistance (R) of the resistor (500 ohms) and the voltage across it (12 volts). So, we can use the formula V = IR to calculate the current (I) flowing through the resistor.

V = IR
12 volts = I * 500 ohms
I = 12 volts / 500 ohms
I = 0.024 amps

Therefore, the current flowing through the resistor is 0.024 amps.

Now, to find the voltage across the transistor, we need to use Kirchhoff's Voltage Law (KVL), which states that the sum of all voltages in a closed loop is equal to zero. In this circuit, the voltage across the resistor is 12 volts, and the voltage across the power supply is 12 volts. This means that the voltage across the transistor must also be 12 volts for KVL to hold true.

So, the voltage across the transistor is also 12 volts.

I hope this explanation helps you understand how to approach this question. Remember to always use the relevant laws and equations when solving electronic circuit problems. Good luck with your practice exams!