In direct coupling or dc coupling, the individual amplifier stage bias conditions are so designed that the two stages may be directly connected without the necessity of dc isolation. For many amplification purposes, a single transistor does not provide enough gain, so multiple circuits, or ´stages of amplification´ are needed. Or, when the gain. What types of optical components might be inserted between stages in a multi-stage amplifier? Why are different mode areas appropriate for different amplifier stages? How does cladding pumping differ from core pumping in fiber amplifiers? How to use multiple pump diodes in a multi-stage amplifier?The solution is to combine multiple stages of amplification. The sections in this chapter tend to use. Amplifiers that produce voltage, current, and/or power gain through the use of two or more stages are called multistage amplifiers. In a multistage. 1- The signal is amplified with gain as in the following equation: ( d I[z ])/(d z) =g I but gain g can be saturated: g= g0/(1+ I(z) /Isat) where g0 is a characteristic value, and Isat, the saturation intensity is: Isat = ( spont/(2 stim)) h n where spont and stim are the. A multistage amplifier is an electronic amplifier consisting of two or more single-stage amplifiers connected together. The most common reason for using.