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有人care過bandgap可能存在不止1個degenerate points(stable points)嗎？
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; P4 U# K2 K8 r% C4 [; rThe degenerate point of Bandgap reference circuit
) N: r+ [0 K) J( T* v+ g \Q:有人care過bandgap可能存在不止1個degenerate points(stable points)嗎？$ I) j5 T& k; w7 p4 K9 o! J/ p* K
A: We do care the degenerate points of a bandgap reference circuit. The bandgap reference circuit needs a more effective startup circuit than those usually adopted. The crossing (degenerate) points are much less defined. Please read the attached bandgap degenerate points.pdf
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: o2 }1 ?& D* t4 Z3 w" H1 L============================================================
: h7 _7 |: y6 K6 w# @* l/ GLow Voltage Bandgap Reference Circuit
$ e/ Z: j- L, u% ] ZPatent number: 6489835
" `3 Q# z% k/ j! i5 s. {Filing date: Aug 28, 2001
" @: c) ]0 }+ y5 Q: K' s( i) WIssue date: Dec 3, 20023 ~. G1 S* Q$ X. w6 B3 L0 o+ p
Inventors: Quan Yu, Edwin Chan9 `5 U- m1 W9 q2 P
Assignee: Lattice Semiconductor Corporation5 E' n/ g! n6 B u2 S1 d
9 S" _$ I4 u8 w; A2 I* j8 k7 nBanba et al, in "A CMOS Bandgap Reference Circuit with Sub-1-V Opeation", discloses a bandgap reference circuit that can operate at supply voltage down to about 1V. This configuration needs two additional resistors, RA and RB, to generate CTAT currents. However, these two resistors will result in more than one opeating point, especially when the drain voltages of PMOS transistors, drops below ΔVbe(i.e., when the two bipolar devices are turns off). Existence of more than one opeating point makes the start-up circuit very complex, or requires an additional circuit to gurantee achievement of a proper operating point. Without such a circuit, the risk of having an undesired operating point is high.
, v$ N9 h& Q. T: J6 IThis configuration differs from Banba's circuit in several ways.
! B# e' b' V- m N$ m s5 z! y1. Only one resistor, RC, is added to provide an CTAT current, rather than need two such resistors.
' c7 d: o" h# P: e1 u2. Only one non-zero initial current, and this system will move to this point after power-up.
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Low_voltage_bandgap_reference_circuit.pdf
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