cascode MOSFET amplifier
1 Answer

A CS-CG cascode connection is shown as follows. this configuration has features of a high input impedance and low voltage gain. it ensures that miller capacitance is at minimum.

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It consist of a common souce amplifier (MOSFET $m_1$) and a common gate amplifier (MOSFET $m_2$)

The input signal is applied to $m_1$, (cs amplifier) and the output is obtained from $m_2$, i.e. from the CG stage. the input resistance and current gain of the cascode configuration are equal to the corresponding value of a single stage CS amplifier. The overall output resistance is equal to that of the CG configuration (typically 2M $\Omega$) The miller capacitance that appears in parallel with CS input stage is very small. this gives a very large value of upper cut off frequency. therefore the bandwidth of the cascode stage is very large. the internal feedback due to inter electrode capacitance's decrease. therefore the possibility of oscillation is reduced.

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