The voltage summing BGR in Figure 2.7 is also composed of three sub circuits. The only
difference between the current summing BGR and the voltage summing BGR is the third
sub-circuit. The third section is composed of a differential amplifier in a non-inverting
feedback loop. The offset voltage from the use of unmatched bipolar transistors generates the
PTAT component. The applied diode voltage is not the full base-emitter voltage, as in a
standard BGR, but a fraction. The minimum supply voltage of one path is VT plus a VCEsat,
plus the source to drain voltage of the current source. The second path’s minimum supply
voltage is a VBE plus the minimum voltage of the current source plus the output voltage of
the VBE generator. This value is equal to 1 V with the technology that was used in this study.