A 50mV signal is applied to the base of a properly biased transistor with r'e=10ohms and RC=560ohms. Determine the signal voltage at the collector.
In my text book for this section there are formulas
Vb=Ier'e
Vc=IcRC
Vc=IeRC
Do I take 50mV/560ohms to get Ic then take that result and multiply by 560ohms to get VC? Not sure where the r'e=10ohms comes into play.
Any help would be much appreciated.
To determine the signal voltage at the collector (VC), you need to first calculate the collector current (IC). To do this, you can use Ohm's Law. Since the base-emitter voltage (Vbe) is not provided, we can assume it to be about 0.6-0.7V for a forward-biased transistor.
Here's how to calculate the collector current:
1. Find the base current (IB):
- IB = Vb / r'e (using the formula Vb = Ie * r'e)
2. Find the collector current (IC):
- IC ≈ IB (assuming β is large, and most of the current is contributed by IC)
Now, to calculate the signal voltage at the collector (VC), you can use the relationship given in your textbook:
VC = IC * RC
Substitute the value of IC you just calculated into this equation, and multiply it by the value of RC (which is 560 ohms) to get the answer.
Note: The value of r'e (which is the dynamic input resistance, also known as the effective base-emitter resistance) comes into play in determining the base current (IB) through the relation Vb = IB * r'e.