1.2 GHz VCO with Kinear Modulation

Since high frequency voltage-controlled oscillators, or VCOs, are not easy to construct, Maxim (www.maxim-ic.com) has produced an integrated 1.2 GHz oscillator, the MAX2754. The centre frequency is set using the TUNE input, and a linear modulation input allows the frequency to be modulated. The IC is available in an 8-pin µMAX package, operates from a supply of between 2.7 V and 5.5 V, and draws a current of less than 20 mA.Both TUNE and MOD operate over control voltage range of +0.4 V to +2.4 V. TUNE allows the VCO frequency to be adjusted from 1050 MHz to 1270 MHz. In some applications a PLL control voltage will be applied here, allowing the centre frequency to be set exactly to a desired value. For simplicity in the circuit diagram we have shown a potentiometer.