Common emitter BJT Amplifier - maximum input voltage

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The discussion focuses on calculating the maximum input voltage for a common emitter BJT amplifier to ensure proper amplification without distortion. Key parameters include a β of 100, VCE saturation of 0.2V, and a calculated gain of Av=-115.7. It is emphasized that the Q point of the BJT should ideally be centered between saturation and cutoff to maximize the range of signals without distortion. Participants suggest that if the input voltage exceeds a certain threshold, the amplifier may enter saturation or cutoff, leading to distortion. Understanding the load line and Q point positioning is crucial for determining the maximum input voltage.
etf
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Here is my circuit:
β=100, VCEsaturation=0.2V, VBE=0.7V, λ->0, VT=26mV

kolo.jpg


After completing DC analysis I got these results :
IB=18.05μA, IC=1.805mA, IE=1.823mA, VCE=4.658V>VCEsaturation=0.2V, gm=0.06943, rCE=∞ Ω, rpi=1.44kΩ.
After completing AC analysis I got Av=-115.7, Ai=72.23, Rin=1.040kΩ, Rout=1.67kΩ.
How to calculate maximum input voltage for proper amplification (without distortion I mean) ?
 
Last edited:
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etf said:
Here is my circuit:
β=100, VCEsaturation=0.2V, VBE=0.7V, λ->0, VT=26mV

View attachment 68124

After completing DC analysis I got these results :
IB=18.05μA, IC=1.805mA, IE=1.823mA, VCE=4.658V>VCEsaturation=0.2V, gm=0.06943, rCE=∞ Ω, rpi=1.44kΩ.
After completing AC analysis I got Av=-115.7, Ai=72.23, Rin=1.040kΩ, Rout=1.67kΩ.
How to calculate maximum input voltage for proper amplification (without distortion I mean) ?

What are your thoughts on this? You have calculated the gain, and you have an idea of where saturation is -- how can you use this? Is the output centered naturally between saturation and cutoff? If not, that will decrease the range of signals that can be passed without distortion.
 
I know that Q point of BJT should lie in middle of load line for maximum amplification and if input voltage v(t) is too high then BJT will operate in saturation and cutoff and therefore there will be distortion. I'm still not sure how to use this fact for my calculation :(
 
Last edited:

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