A 20-800 MHz relaxation oscillator with automatic swing control

An automatic swing control (ASC) feedback for relaxation voltage-controlled oscillators (VCO) dynamically monitors capacitor voltage swing and adjusts threshold voltage of the oscillator to maintain the swing at a constant level, providing wide linear frequency range. The ASC-VCO is implemented in 14 GHz f/sub T/ bipolar technology. The circuit has a frequency sweep range from 20 MHz up to 800 MHz, with the upper frequency limit dictated by the value of the delay. The bipolar process offers n-p-n transistors with 14 GHz cut-off frequency and lateral p-n-p transistors with 60 MHz cut-off frequency. The chip consists of the following blocks: a relaxation oscillator with ASC feedback, a voltage-to-current converter, a bandgap voltage generator, trimming circuitry and temperature compensation circuitry.