31-03-2014, 12:38 PM
The low-Frequency Response
Frequency Response.pptx (Size: 277.62 KB / Downloads: 27)
To determine the low-frequency gain or transfer function of the common-source amplifier,
we show in Fig.5(a) the circuit with the dc sources eliminated (current source I open
circuited and voltage source VDD short-circuited). We shall perform the small-signal analysis
directly on this circuit. However, we will ignore ro This is done in order to keep the analysis
simple and thus focus attention on significant issues. The effect of ro on the low-frequency
operation of this amplifier is minor, as can be verified by a SPICE simulation (Section 4.12).
The analysis begins at the signal generator by finding the fraction of Vsig that appears at
the transistor gate.