SESSION XVI: A/D and D/A Techniques
Amy Brokaw · 1973
A CIRCUIT, illustrated in Figure 2, using collector current sensing to reduce errors and provide more flexibility than the conventional bandgap circuit’ will be described. Collector current sensing is used to fix the ratio of current density in two transistors. This ratio generates a temperature-proportional voltage which is added to VBE to produce a temperature-stable sum voltage. Conventional bandgap circuits use parallel current paths with voltage sensing connections between the paths. These circuits are typified by Figure 1, discussed earlier’ to illustrate the operation of more complex, but fundamentally similar circuits. In this well-known circuit parasitic currents exchanged between the parallel paths are not accounted for in the theory and give rise to beta-dependent voltage errors and temperature drift. To generate higher voltages with the conventional circuit, it is necessary to stack junctions to produce a multiple of the bandgap or use a second amplifier to multiply the separately stabilized bandgap voltage.