Analog Electronics with LabVIEW®

10.1. DC (Bias) Circuit

The bias circuit is critical in terms of getting the dc output voltage at a value near the project design value of V_O = V_DD/2 (for maximum output magnitude and linearity). The relation, from the dc circuit analysis, for obtaining this condition is based on I_D1 = I_D2. This is, in terms of the transistor characteristic equations, (3.8),

Equation 10.1

Note that the source-gate voltage of M₂ is referenced to M₃. A certain combination of V_GS1 and V_SS will satisfy V_o = V_DD/2. In the project on the amplifier, a LabVIEW VI sends out a V_G1 = V_GS1 to set up a given I_D1 = I_D2 and then adjusts V_SS to obtain the desired bias output ...