Why Does My BJT Simulation Show Different Collector Current Than Calculated?

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SUMMARY

The forum discussion centers on discrepancies between calculated and simulated collector current (Ic) in a BJT circuit. The user calculated Ic as 22.12mA using the formula Ic=βIb with β=175, while the simulation indicated a value of 1.64mA. The user’s calculations for base current (Ib) were based on Vcc and Vbe, but the circuit's operation in a non-linear region led to incorrect assumptions about Ic being equal to β*Ib. The discussion highlights the importance of understanding transistor saturation and its effects on collector-emitter voltage (Vce).

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1. As compared to the circuit as shown in the figure, i applied KCL in the circuit and still couldn't get the right Ic current at the collector as shown in the simulation.

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2. The IC current for XMM2 is 1.64mA but i got 22.12mA instead in my calculation. (I'm using the Ic=βIb where β=175 for the solution.)



3. Ib= Vcc-Vbe/20k Ib=3-0.7/20k Ib=0.115mA Ic=Ib (175) Ic=22.12mA

Any idea? Somehow, i need to explain it in my discussion for my report. I screwed up with the calculation and i have no idea of explaining the reason why Vce is approximately equal to 0 when there is a Ib current due to Vb voltage at its base.

More info, XMM1 shows the voltage of 77.205mV...
 
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You're operating the transistor in a non-linear region. Ic will not be β*Ib there.

Suppose that the transistor was driven into saturation (turned on as hard as it can go). Then the collector-emitter voltage would be just about zero (looks like an "ON" switch). What would be the voltage across R1? What then its current?
 

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