The voltage gain can be easily calculated for all transistor connection types as we've seen in the previous pages. There is another simpler method to calculate the power gain through the voltage gain, using the h fe parameter. Regarding the input power calculation, we will apply the same formula, but this time on the base of the transistor:Ĭalculating the power gain using the hfe parameter Remember again that we are talking about the voltage on the load, and since the load is coupled through a capacitor, it can only be an AC voltage. For the output power calculation, we only need to apply this formula to the load: Usually, the last one with the peak-to-peak voltage is used. For both cases we will use one of the formulas for the power calculation from above. So we need to calculate the power on the output and on the input of the circuit.
The formula to calculate the power gain is typical: The above formula can be directly converted to use peak-to-peak values like this: If you are using an oscilloscope, then you need to convert the voltage from peak-to-peak into rms. The above formula is valid if the voltage is measured with a volt-meter. We can apply the Ohm's law (I = V / R) on the above formula to extract a more practical one: We will use the typical V x I formula with the rms values for voltage and current: Now let's see how we can calculate the power of the input and the output signal.
#POWER DISSIPATION BJT TRANSISTOR HOW TO#
So, depending on which measuring method you use, you may need to know how to convert between rms and p-p (peak-to-peak): That is because the voltmeter measures the rms-voltage while the oscilloscope measures the peak-to-peak voltage. If you measure the same signal with a voltmeter and an oscilloscope, you will not get the same results. Since we are talking about AC values, there is something first that we need to make clear: There are two ways to measure a AC sizes -for example voltage-, using an rms volt-meter or using an oscilloscope. How to do conversions between peak-to-peak (p-p) and rms sizes This includes both the input and output signal power, the power gain of the circuit, the efficiency and the power dissipation on the transistor. It is important to be able to calculate the power characteristics of a transistor circuit.
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