Simulate the band-gap reference from Problem 4.29 on SPICE. Assume that the amplifier is just a voltage-controlled voltage source with an openloop gain of 10,000 and that the resistor values are independent of temperature. Also assume that I_S1= 1.25 × 10^ˆ’17A and I_S2= 1 × 10^ˆ’16A. In SPICE, adjust the closed-loop gain of the amplifier (by choosing suitable resistor values) so that the output TC_Fis zero at 25 °C. What is the resulting target value of V_OUT? Now double I_S1and I_S2. Use SPICE to adjust the gain so that V_OUTis equal to the target at 25 °C. Find the new dV_OUT/dT at 25 °C with SPICE. Compare this result with the calculations from Problem 4.29.

Data from Prob. 4.29:

A band-gap reference like that of Fig. 4.47 is designed to have nominally zero TC_F at 25°C. Due to process variations, the saturation current I_S of the transistors is actually twice the nominal value. Assume V_OS = 0. What is dV_OUT/dT at 25 °C? Neglect base currents.

Fig. 4.47:

Transcribed Image Text:

Vos R2 :R3 VOUT Q2