How to choose Hfe in common emmiter amplifier circuit

  • Thread starter Thread starter null void
  • Start date Start date
  • Tags Tags
    Amplifier Circuit
AI Thread Summary
When constructing a common emitter amplifier circuit using the BC107bp transistor, it's essential to choose the appropriate Hfe value based on the collector current. For a collector current of 1mA, selecting an Hfe of 200 is advisable, as it provides a balance between performance and stability. The choice of Hfe can significantly impact the amplifier's frequency response and input impedance, depending on the configuration used. Conducting a worst-case analysis is recommended for design engineering, while beginners should start with average values and explore parameter extremes for educational purposes. Understanding these variations is crucial for effective circuit design.
null void
Messages
102
Reaction score
1
I am using a transister model BC107bp in multisim, and i found that its min Hfe is 40 and max Hfe is 450. If I want to construct an amplifier circuit, i should choose the min or average? I found most of the datasheet show the hfe of collector current at 2m A (min 200 - max 450), but if my collector current is 1mA, should i choose the min Hfe which is 40? Any suggestion?
 
Last edited:
Engineering news on Phys.org
It depends on the amplifier configuration.
If it is a common emitter amplifier then high frequency response will be hurt by a high Hfe.
If it is a common base amp it will not be sensitive to Hfe variation.
If it is common collector, (emitter follower), then input impedance will be affected by Hfe variation.

Design engineering requires that you perform a worst case analysis where all parameters vary. A student or hobbyist should start modelling with average values, then test some parameter extremes as a learning exercise. Explaining the changes observed with parameter changes will be highly educational.
 
  • Like
Likes 1 person
For the Ic = 1mA you shoudl choose hfe = 200.
 
Thread 'Weird near-field phenomenon I get in my EM simulation'

Thread 'Weird near-field phenomenon I get in my EM simulation'

I recently made a basic simulation of wire antennas and I am not sure if the near field in my simulation is modeled correctly. One of the things that worry me is the fact that sometimes I see in my simulation "movements" in the near field that seems to be faster than the speed of wave propagation I defined (the speed of light in the simulation). Specifically I see "nodes" of low amplitude in the E field that are quickly "emitted" from the antenna and then slow down as they approach the far...
View full post »

Thread 'EMF (Electromagnetic Field) & EHS (Electromagnetic Hyper Sensitivity)'

Hello dear reader, a brief introduction: Some 4 years ago someone started developing health related issues, apparently due to exposure to RF & ELF related frequencies and/or fields (Magnetic). This is currently becoming known as EHS. (Electromagnetic hypersensitivity is a claimed sensitivity to electromagnetic fields, to which adverse symptoms are attributed.) She experiences a deep burning sensation throughout her entire body, leaving her in pain and exhausted after a pulse has occurred...
View full post »

Similar threads

Troubleshooting LM311P Output Issue - Tips and Suggestions
Replies
1
Views
1K
How to choose an amplifier to couple the noise into data line
Replies
2
Views
1K
How do I analyze an audio amplifier circuit?
Replies
7
Views
2K
Trouble understanding common-emitter amplifiers
Replies
17
Views
3K
Where to Learn how to Design Circuits?
Replies
7
Views
2K
Amplify Position Sensor Circuit
Replies
6
Views
2K
Capacitors in Common Emitter Amplifier Circuit ?
Replies
1
Views
10K
What is a good Overdrive Factor for a BJT?
Replies
5
Views
14K
Help with bjt amplifier design
Replies
1
Views
3K
How to Design a Microvolt Pulse Detector Circuit with High Gain and Low Noise
Replies
6
Views
2K

Hot Threads

Recent Insights

Back
Top