Patent ID: 7205813
Filing Date: 2007-04-17
Classification: H03K

Abstract:
1. A differential type delay cell comprising: a differential amplifier that is configured to amplify a differential input signal to generate an amplified differential output signal at a pair of output nodes of the delay cell; and first and second output capacitor circuits that are respectively coupled to different ones of the output nodes, and are configured to have a variable capacitance that varies in response to variation in a power supply voltage, and wherein: the first and second output capacitor circuits each include at least one MOS capacitor; the first and second output capacitor circuits further comprise a bias voltage generator that is configured to generate a bias voltage for biasing the at least one MOS capacitor; the MOS capacitor of each of the first and second output capacitor circuits comprises a plurality of electrodes, one of the electrodes is coupled to the bias voltage and another one of the electrodes is coupled to one of the output nodes; and the bias voltage generator is configured to generate the bias voltage to bias the MOS capacitor of each of the first and second output capacitor circuits near a threshold voltage of the MOS capacitors, and the bias voltage generator comprises: a voltage controlled current source configured to generate a variable current that varies responsive to a control voltage; and a load element, wherein the load element and the voltage controlled current source are coupled in series between the power supply voltage and ground, and wherein the bias voltage is generated from a node between the voltage controlled current source and the load element.