In the bias portion of the CA1340 op-amp in Figure 13.22, the bipolar transistor parameters are \(V_{B E}(\mathrm{npn})=0.6 \mathrm{~V}\) and \(V_{E B}(\mathrm{pnp})=0.6 \mathrm{~V}\) and the MOSFET parameters are \(V_{T P}=-1.2 \mathrm{~V}\) and \(K_{p}=0.15 \mathrm{~mA} / \mathrm{V}^{2}\).

(a) Determine the currents \(I_{1}=I_{2}\).

(b) If the bias voltages are \(V^{+}=-V^{-} \equiv V_{S}\), determine the minimum value of \(V_{S}\) such that the bias currents are independent of the supply voltage.

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V+ Di 26 21 R = IRI 8 VSG + Mg VSD D VD Figure 13.22 Bias circuit, CA3140 BiCMOS op-amp