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CACD Group updated 2000.03.30 Author Janez Puhan |
Low DC Voltage StabilizationThe circuitRealising stabilised dc voltages below a zener boundary of about 2V is difficult. Higher voltages may be reduced by ohmic voltage dividers, but too much of the power must be dissipated if the resistors need to be at low values. A 1.5V zener diode can be simulated by a complementary pair of bipolar transistors having zero dynamic impedance. In the case of r2 = 0, both transistors are like two diodes connected in series. If r2 is omitted a regenerative process starts which leads to a negative resistance characteristic similar to tunnel diodes. Between these two extremes, an adjustment may be found for which the resulting impedance is zero over an extended current range. The coefficient of the temperature is approximately
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