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Current GainAuthor: Leonard Krugman The current gain, , when the circuit is working into the load R_{L}, becomes the ratio of equation 34 to equation 33
and in terms of the openrcircuit parameters, the current gain is the ratio of equation 36 to equation 35
The current gain as derived in equations 37 and 38 indicates the effect of the load resistance R_{L} on α, but does not take into account the effect of mismatch between the signal generator resistance and the input resistance of the transistor. It is evident that the maximum current gain is obtained when the load resistance R_{L} = O. Thus, the maximum
Since r_{b} is very small in comparison with either r_{m} or r_{c}, it may be neglected in equation 38A, and a rather accurate estimate of the maximum current gain is
A frequently used form for the current gain, which incorporates the maximum current gain a_{o}, is


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