TWO COMPONENT LOW TC VOLTAGE BIAS CIRCUIT
Original Publication Date: 1980-Aug-01
Included in the Prior Art Database: 2001-Oct-10
Many circuits employ current sources proportional to temperature (and a reference resistor) to com- pensate for certain parametric temperature shifts (i.e., weighted V~O matching, diff-amp gain, etc.). When this current flows in a resistor (matching the reference resistor), a voltage is developed that is propor- tional to temperature, independent of TCR. Since the voltage drop in a diode junction is inversely propor- tional to temperature, the series conbination with the resistor voltage drop will generate a near zero TC voltage at a certain resistor current level. That level occurs when the series voltage, Va, is approximtely 1.4 V. The major source of error is the sensitivity of the diode to current changes. This accounts for a 64 ppm/'C temperature drift of Vt.. This low TC voltage can be used as a very inexpensive (two component) spot regulator for whenever any combination of 1.4 V bias voltages is needed (i.e., lTL level threshold, reference for more complex regulator).