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#1 Feb 20, 2017
OpPi
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Strange Bode-Plot behavior

Hey,

I'm trying to design a simple Common Emitter amplifier and analyze its Bode plot. For some reason, my amplifier behaves not as a BPF but as a HPF, having only a lower cutoff frequency but not upper one. Added are the amplifier and Bode plot:

Also, I must not touch any of the QbreakN parameters or use any other transistor.

Thanks

Mon, 2017-02-20 22:37
alok
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Why do you say - I must not touch any of the QbreakN parameters or use any other transistor? Assuming your circuit component values are correct and should behave as BPF - if you need to select proper transistor so that it get appropriately biased to behave as designed. In other words is your circuit designed to work independently of transistor characteristics?

Tue, 2017-02-21 03:26
RobertoGb
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Hi OpPi,

With your comment, I suppose you need to design a BPF withouth changing or adding any parameters to QbreakN. Is it right? 

If it is so, please take into account the high frequency response equations and the features of the QbreakN and introduce a small Miller capacitor CF between Collector and Basis to control the high frequency 3-dB response of the amplifier. Using a 1n capacitor, you are getting a HF of of approximately 75 KHz.

 

 

 

I hope this helps

Tue, 2023-07-11 06:03
dansonpas
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I don't see why you're insisting that I can't adjust the QbreakN settings or swap out the transistor. Assuming the component values in your circuit are accurate, the BPF behavior can be achieved by selecting the proper transistor and applying the necessary bias. Does your circuit not rely on specific transistor properties for operation? drift boss

Sat, 2023-09-16 05:51
kunaal
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