Depletion-mode FET for the regulation of the on-chip generated substrate bias voltage
First Claim
1. In an integrated circuit having a semiconductor substrate, a voltage generator for providing a substrate bias voltage for the substrate, the voltage generator comprising:
- a depletion-mode field-effect transistor having a source for receiving a reference voltage, a gate for receiving the bias voltage, and a drain;
a ring oscillator comprising an odd number of at least three inverters serially arranged in a ring, the inverters providing a pair of complementary signals that repetitively vary when the transistor is conductive;
a charge pump responsive to the complementary signals as they repetitively vary for pumping the bias voltage to a value (1) less than the sum of the reference voltage and the threshold voltage of the transistor where it is N-channel type or (2) greater than the sum of the reference voltage and the threshold voltage of the transistor where it is P-channel type; and
means for stopping the oscillator from oscillating when the transistor is non-conductive so that the bias voltage (1) increases where the transistor is N-channel type or (2) decreases where the transistor is P-channel type.
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Accused Products
Abstract
An on-chip regulated substrate bias voltage generator for an MOS integrated circuit includes a ring oscillator (10) for developing a true signal and its complement. The signals are applied to a charge pump (12) that includes two capacitors (C1 and C2) and a plurality of rectifiers (22, 24, and 26). The charge pump produces a substrate bias voltage (VBB) which is supplied to the gate of a depletion-mode field-effect transistor (28) whose source receives a reference voltage (VSS). The transistor forms part of a control circuit (14) coupled to the ring oscillator. In the N-channel case, the charge pumping action on the substrate drives the substrate bias negative until it reaches the sum of the reference voltage and threshold voltage of the depletion-mode transistor. This enables the control circuit to control the operation of the ring oscillator so as to regulate the substrate bias voltage.
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Citations
10 Claims
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1. In an integrated circuit having a semiconductor substrate, a voltage generator for providing a substrate bias voltage for the substrate, the voltage generator comprising:
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a depletion-mode field-effect transistor having a source for receiving a reference voltage, a gate for receiving the bias voltage, and a drain; a ring oscillator comprising an odd number of at least three inverters serially arranged in a ring, the inverters providing a pair of complementary signals that repetitively vary when the transistor is conductive; a charge pump responsive to the complementary signals as they repetitively vary for pumping the bias voltage to a value (1) less than the sum of the reference voltage and the threshold voltage of the transistor where it is N-channel type or (2) greater than the sum of the reference voltage and the threshold voltage of the transistor where it is P-channel type; and means for stopping the oscillator from oscillating when the transistor is non-conductive so that the bias voltage (1) increases where the transistor is N-channel type or (2) decreases where the transistor is P-channel type. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification