How to choose Hfe in common emmiter amplifier circuit

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SUMMARY

The discussion centers on selecting the appropriate Hfe value for a common emitter amplifier circuit using the BC107bp transistor model in Multisim. The minimum Hfe is 40, while the maximum is 450, with datasheets indicating an Hfe of 200 at a collector current of 2mA. For a collector current of 1mA, it is recommended to use an Hfe of 200 to ensure optimal performance. The choice of Hfe significantly impacts amplifier configurations, particularly affecting high-frequency response in common emitter setups.

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  • Understanding of transistor parameters, specifically Hfe.
  • Familiarity with common emitter amplifier configurations.
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Electronics students, hobbyists, and design engineers interested in amplifier circuit design and optimization, particularly those working with transistor parameters and simulation tools like Multisim.

null void
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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?
 
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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.
 
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For the Ic = 1mA you shoudl choose hfe = 200.
 

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