Oki Electric Industry Co., Ltd.

Oki Semiconductor Co., Ltd.

Yuko Murase

Ken Fujita

A reference current generator for outputting a current proportional to absolute temperature includes a fixed current source transistor, a variable current source transistor and an output transistor which are connected to a drain voltage line. The fixed current source transistor is connected to a source voltage via a series of resistor and first diode. The variable current source transistor is connected to the source voltage via a second diode. A first node between the variable current source transistor and the resistor is connected with a noninverting input of an operational amplifier, and a second node between the variable current source transistor and the second diode is connected with an inverting input of the operational amplifier. The operational amplifier has its output connected to the gate electrode of both the fixed current source transistor and the output transistor, which outputs a PTAT current depending upon the gate voltage.

Reference current generator adjustable by a variable current source

A voltage controlled oscillator includes a resonant circuit, a trimming capacitor and a full adder. The resonant circuit includes a negative resistor, an inductor and an oscillation frequency setting capacitor having a variable capacitance according to a controlled voltage based on a oscillation frequency data. The trimming capacitor is connected in parallel to the oscillation frequency setting capacitor. The trimming capacitor has capacitors each of which has a variable capacitance according to an input signal thereof. The full adder is connected to the trimming capacitor. The full adder generates the input signal based on frequency information and an automatic proofreading value received thereto.

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Tokyo, Japan

Yuko Murase