Analog Electronics with LabVIEW®

2.3. Basic NMOS Common-Source Amplifier

An example of the application of the transconductance relation for the transistor is the basic circuit in Fig. 2.4. Setting dc voltages (in this case, V_DD) equal to zero in Fig. 2.4(a) leads to the signal (or ac) circuit [Fig. 2.4(b)]. This follows from the fact that the signal circuit involves only incremental variables (changes) and V_DD is a constant.

The schematic symbol for the transistor in the signal circuit associates the output current with the input voltage according to the linear relation of (2.3). For linear circuit analysis, the linear equivalent circuit of Fig. 2.2 (Fig. 2.4(c)) replaces the linear schematic-symbol representation [Fig. 2.4(b)]. For the MOSFET, r_in is infinite and therefore ...