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Substrate biasing circuit having controllable ring oscillator

  • US 5,808,505 A
  • Filed: 09/05/1997
  • Issued: 09/15/1998
  • Est. Priority Date: 05/25/1993
  • Status: Expired due to Fees
First Claim
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1. A substrate biasing circuit comprising a charge pump circuit receiving a drive pulse signal and generating a substrate-bias voltage at an output terminal in response thereto, said charge pump circuit including an output transistor coupled to said output terminal to output said substrate-bias voltage, a ring oscillator including a plurality of delayed-inverter circuits connected in a ring form to produce said drive pulse signal, said drive pulse signal having a frequency, and a current control circuit controlling each of said delayed-inverter circuits such that the frequency of said drive pulse signal is increased when a threshold voltage of said output transistor is larger than a predetermined value and is decreased when said threshold voltage of said output transistor is smaller than said predetermined value.

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