发明授权
US06429702B2 CMOS buffer for driving a large capacitive load 有权
用于驱动大容性负载的CMOS缓冲器

  • 专利标题: CMOS buffer for driving a large capacitive load
  • 专利标题(中): 用于驱动大容性负载的CMOS缓冲器
  • 申请号: US09345059
    申请日: 1999-06-30
  • 公开(公告)号: US06429702B2
    公开(公告)日: 2002-08-06
  • 发明人: Dima David Shulman
  • 申请人: Dima David Shulman
  • 主分类号: H03F326
  • IPC分类号: H03F326
CMOS buffer for driving a large capacitive load
摘要:
A class AB buffer (or amplifier) is disclosed for driving a large capacitive load. The disclosed CMOS class AB buffer can drive capacitive loads, for example, in excess of 100 pF, while operating from a voltage supply as low as 1.5 volts. The disclosed class AB buffer includes a pair of driving transistors that are cross-coupled through an amplifier and level shifting circuitry, such as transistor circuitry, and a pair of current source transistors each having a gate terminal connected to an output of the corresponding amplifier and a gate terminal of an output transistor, and a drain terminal connected to a source terminal of the driving transistors. The driving transistors are prevented from entering a linear region by connecting a drain terminal of each of the driving transistors to a positive power supply voltage. The threshold voltage of only one transistor must be overcome before the transistors conduct current, since the gate-sources of the driving and current source transistors are not in series. Performance enhancements may be achieved by using cascode transistors in the input stage or output stage, or both. The stability of the circuit is ensured by selecting the capacitance of the load to ensure that a first non-dominant pole of the class AB buffer is greater than the unity gain bandwidth of the class AB buffer over substantially all operating conditions.
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