It is shown that three different approaches to calibration technique based on the use of average cross-section, equivalent
target thickness and thick target yield are adequate. Using the concept of thick target yield, a convenient charged particle
activation equation is obtained. The possibility of simultaneous determination of two elements impurities, from which the
same isotope is formed, is pointed out. The calibration technique, in which thin standard is used but activation curve is
not required, is discussed.