Document Type and Number:
Japanese Patent JPH0243369
Kind Code:
B2
Abstract:
An integrated circuit voltage controlled oscillator (VCO) consists of an astable multivibrator with external fixed components resistor RT and capacitor CT. The multivibrator has a centre frequency timed by constant currents I1 charge and discharge of capacitor CT. The period timed is proportional to VT/I1 where VT is half the voltage swing of capacitor CT. …A voltage source VZ is generated from the voltage supply VS which supplies two networks N1, N2 associated with the multivibrator. Network N1 including resistor RT generates two constant currents I1 for charge and discharge of timing capacitor CT. Network N2 generates a voltage VT which is buffered into the multivibrator circuit and arranged to control the voltage swing of capacitor CT. Networks N1 and N2 are similar matched transistor/resistor networks track each other whereby variations in VCO centre frequency due to manufacturing tolerances, temperature changes and supply voltage variations are minimised. When an asymmetric output waveform is required unequal constant currents I1 I2 are generated by network N1. …A control voltage VC for varying the VCO frequency acts via a differential amplifier to vary the voltage applied to network N1 above or below the voltage source VZ to increase or decrease the constant currents I1 (or I2). The voltage gain of the differential amplifier is determined by the quotient of two resistor values which track each other to minimise variations of the gain of the VCO with temperature.
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Application Number:
JP6077780A
Publication Date:
September 28, 1990
Filing Date:
May 09, 1980
Export Citation:
International Classes:
C03C17/34; H03K3/282; H03K4/50; H03K7/06; H03L1/00; H03L7/099