Patent ID: 7777477
Filing Date: 2010-08-17
Classification: G01R

Abstract:
1. A frequency characteristic measuring circuit, wherein the frequency characteristic is based on a relationship between an oscillating frequency of a voltage controlled oscillator and a measurement result of a quantity of heat from the voltage controlled oscillator, the circuit comprising: a first diode element driven by a first constant current source, wherein the first diode element is thermally coupled to a first resistance element of a differential amplifying circuit, and wherein the resistance element of the differential amplifying circuit is connected between differential output nodes of the differential amplifying circuit, and wherein the differential amplifying circuit is a receiving circuit or a transmitting circuit provided in an I/O circuit of a semiconductor integrated circuit for high-speed signal transmission; a second diode element used as a reference, driven by a second constant current source; and a detection circuit which detects a potential difference between forward voltages of the first and second diode elements, and outputs a signal that is a function of the detected potential difference, the output signal being an indication of the quantity of heat produced by the voltage controlled oscillator during operation.