Temperature stable BiCMOS voltage-to-frequency converter

A BiCMOS temperature stable voltage-to-frequency converter is described. The circuit includes an input voltage-to-current conversion stage followed by a voltage-controlled current switch. The switch is controlled by a nonsaturated multivibrator with a limiter of the output voltage swing. The multivibrator thresholds are stabilized using a current produced in a bandgap voltage reference. This allows one to obtain high resolution near both trigger thresholds. The difference between simulated and calculated characteristics is less than 5% in the range 0.5 to 2 V of the input signal (for 5 V power supply voltage). The temperature variation of sample oscillation frequencies for this range of input signal was less than 2% in the temperature range -25/spl deg/C to 75/spl deg/C. The converter is under fabrication using BATMOS process.