Analog Electronics with LabVIEW®

3.3. Body Effect and Threshold Voltage

In Fig. 3.4 is shown an example of a circuit in which the body and source cannot be at the same voltage. We now use the four-terminal symbol for the NMOS, which includes the body contact. In most applications, the body would be tied to the lowest potential in the circuit (NMOS), in this case, V_SS (e.g., V_SS = –5 V). But by the nature of the circuit, the source voltage is V_S = V_SS + I_DR_S, such that the source-body voltage is V_SB = I_DR_S.

Figure 3.4. NMOS transistor circuit with a resistor, R_S, in the source branch. With the body attached to V_SS, V_SB = I_DR_S.

In MOSFET devices, the threshold voltage depends ...