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Amplification Factor, Plate Resistance, and TransconductanceAuthor: E.E. Kimberly The plate current of a triode in its circuit may be made to change by changing either the plate voltage or the grid potential. The amplification factor relates these two functions. If, from a given operating point on the mutual characteristic, a change of grid voltage Δe_{c} results in a change of plate current Δi_{b} and a subsequent change of plate voltage Δe_{b} will restore the plate current to its original value, then the amplification factor is
For example, if a change of 40 volts on the plate will restore a platecurrent change caused by a change of + 2 volts on the grid, the amplification factor is 20. The plate resistance rp is found by dividing a small change in plate voltage by the accompanying change in plate current (in amperes). The gridplate transconductance or mutual conductance gm is found for any fixed plate voltage by dividing a small change in plate current Δi_{b} by the change in grid voltage Δe_{c} that produced it. Therefore, and where g_{m} is in mhos and r_{p} is in ohms.


Home Electronic Devices Amplification Factor, Plate Resistance, Transconduct. 