Aband-gap reference circuit is shown in Fig. 4.63. Assume that β F , VA, I S1 = 1 à 10 15 A, and I S2

Aband-gap reference circuit is shown in Fig. 4.63. Assume that β_F†’ ˆž, VA†’ˆž, I_S1= 1 × 10^ˆ’15A, and I_S2= 8 × 10^ˆ’15A. Assume the op amp is ideal except for a possibly nonzero offset voltage V_OS, which is modeled by a voltage source in Fig. 4.63.

(a) Suppose that R₂ is trimmed to set V_OUT equal to the target voltage for which dV_OUT/dT = 0 at T = 25 °C when V_OS = 0. Find dV_OUT/dT at T = 25 °C when V_OS = 30 mV.

(b) Under the conditions in part (a), is dV_OUT/dT positive or negative? Explain.

Fig. 4.63:

R2 Vos R1 1 k Q2 VOUT R3 1 k2