带隙基准作业

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Explain briefly why the circuit in Fig. 11.8 can be temperature-independent.

Figure 12.8 Conceptual generation of temperature-independent voltage Suppose we somehow force $V_{O 1} = V_{O 2}$ , then $I R = V_{B E 1} - V_{B E 2} = V_{T} \ln n$ . Thus, $V_{O 2} = V_{B E 2} + V_{T} \ln n$ . Because $V_{B E 2}$ has a negative TC and $V_{T} \ln n$ has a positive TC, $V_{O 2}$ might have a zero TC.

12.7 Consider the self-biased cascode shown in Fig. 12.44. Determine the minimum and maximum values of $R I_{REF}$ such that both $M_{1}$ and $M_{2}$ remain in saturation

Figure 12.44 Solution: To make $M_{1}$ remain saturation,

V_{D 1} - V_{G 1} \leq | V_{TH1} | \Rightarrow R I_{REF} \leq | V_{TH1} |

To make $M_{2}$ remain saturation

V_{G 1} + | V_{G S 1} | - V_{G 2} \leq | V_{TH2} | \Rightarrow R I_{REF} \geq | V_{G S 1} | - | V_{TH2} |

In summary,

| V_{G S 1} | - | V_{TH2} | \leq R I_{REF} \leq | V_{TH1} |

带隙基准