Chapter 13, Problem 13.59P

In the LF155 BiFET op−amp in Figure 13.25, the combination of $Q_3{J}_6$ , and $Q_4$ establishes the reference bias current. Assume the power supply voltagesare $V^{+}=10\text{V}$ and $V^{-}=-10\text{V}$ .Thetransistor parameters are $V_{EB}\left(\text{on}\right)=0.6\text{V}$ , $V_{BE}\left(\text{on}\right)=0.6\text{V}$ , and $V_P=4\text{V}$ for $Q_3,Q_4$ , and $J_6$ , respectively.Determine the required $I_{DSS}$ value for $J_6$ to establish a reference current of $I_{\text{REF}}=0.8\text{mA}$ .