A bipolar monolithic analog-to-pulsewidth converter

A precision analog-to-pulsewidth converter has been achieved with pulsewidth modulation technique and new circuit designs applied to a standard bipolar monolithic IC process. The magnitude and polarity of the input Information are determined by the pulsewidth modulated output signal within 0.002-percent linearity error and 10 PPM/°C full-scale and zero-scale drift at low conversion rate. Although the low-frequency noise in EC buffer limits the actual resolution of the converter to 13 bits, the externally connected Zener diode in EC output reduces the EC noise, and the resolution increases to 15 bits which is consistent with the linearity of the converter.