How can I calculate R1 and R2 values for this transistor biasing circuit?

In summary, to calculate the biasing network for this circuit, you need to use the given values of collector current (10mA) and voltage (10V) as well as the supply voltage (16V) and DC current gain (hFE=80). First, calculate the base current using Hfe, then use the voltage across R2 (16V - 10V) to determine its value. Next, use the voltage across R1 (10V - 0.7V) and the base current to calculate the value of R1.
  • #1
aim1nonly
1
0
Hi guys,

I am trying to find a way to calculate biasing network for the attached circuit.

Basically I need to find R1 and R2 values for operating point of I0 = 10mA and V0 = 10V and Vs = 16V.
DC current gain is assumed to be hFE=80.

How do you calculate R1 and R2 based on these info? Please let me know.

Thanks in advance!
 

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  • #2
You know the collector current Io so you can work out the base current from Hfe.

So, this total current (Io + Ib) passes through R2 and you know the voltage across R2 (16 - 10) so you can work out R2.

Then, you know the voltage across R1 (10 -0.7) and you know the current flowing in it (Ib) so you can work out the value of this resistor.
 

1. What is a transistor biasing circuit?

A transistor biasing circuit is a circuit that is used to establish and maintain a stable operating point for a transistor. It provides the necessary DC voltage and current to keep the transistor in the active region, allowing it to amplify signals.

2. Why is transistor biasing necessary?

Transistors are semiconductor devices that require a specific amount of voltage and current to operate properly. Without proper biasing, the transistor may not function as desired and could potentially be damaged. Biasing also helps to improve the linearity and stability of the transistor's output.

3. What are the different types of transistor biasing?

There are three main types of transistor biasing: fixed bias, collector feedback bias, and emitter bias. Fixed bias uses a voltage divider network to set the base bias voltage, while collector feedback bias uses negative feedback to stabilize the collector current. Emitter bias, also known as self-bias, uses a resistor in the emitter circuit to set the base bias voltage.

4. How do you calculate the values for a transistor biasing circuit?

The values for a transistor biasing circuit can be calculated using the transistor's datasheet and standard circuit analysis techniques. The DC load line must be drawn to determine the operating point, and then the values of the resistors and capacitors can be calculated based on the desired operating conditions.

5. What are the potential problems with transistor biasing circuits?

One potential problem with transistor biasing circuits is thermal instability. This occurs when the temperature of the transistor changes, causing the operating point to shift. Another issue is that biasing circuits can be affected by changes in the transistor's characteristics over time, which can lead to a shift in the operating point. These problems can be mitigated by using carefully selected components and proper circuit design techniques.

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