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Does transconductance (Gm) have 3dB bandwidth

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matrixon

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The voltage gain of an amp is Gm*Zout,
the bandwidth of the voltage gain is limited by the Zout as signal freq increases.
I wonder whether the Gm also has 3dB bandwidth or not.
And If Gm has 3dB bandwidth,what element cause it?
 

Low frequencies have their gain reduced when a coupling capacitor has a higher reactance than the resistance it feeds.
High frequencies have their gain reduced when the output impedance of a transistor is loaded with a capacitance with a reactance that is lower. The capacitance can be the output capacitance of the transistor itself and/or stray capacitance. Therefore gm has a -3dB bandwidth.
 

More than that, the current gain of a BJT as well as the corresponding transconductance gm decrease with rising frequecies due to a decreased mobility of the charged carriers (inertia).
 

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