A voltage compensated series-gate bipolar circuit operating at sub-2 V

A low-voltage series-gate (LSG) bipolar circuit is proposed. A lower-input transistor of the series-gate circuit acts as a current source transistor. The lower-input is driven by a VEE-traced buffer (VTB). The DC characteristics of the VTB output trace the change in a power supply voltage VEE. The switching current of the series-gate circuit is stable while VEE changes. The design of the VTB also takes the temperature variation into consideration. A 4-b counter using this circuit technology is fabricated with 0.8-μm double polysilicon self-align process. The maximum operating frequency of 640 MHz is obtained at -2.0 V and 25°C. The power dissipation of the 4-b counter is 3.3 mW. The circuit operates at over 500 MHz with the supply voltage of -1.6 V. The variation of VEE or temperature has a small effect on the circuit operation