Datasheet

µA78Lxx
V
O
V
I
µA78Lxx
V
O
V
I
-V
O
1N4001
or
Equivalent
µA78L15
0.1 µF
1N4001
0.1 µF
1N4001
0.33 µF
0.33 µF
1N4001
1N4001
V
O
= 15 V
V
O
= -15 V
20-V Input
-20-V Input
µA79L15
μA78L00
www.ti.com SLVS010U –JANUARY 1976–REVISED MAY 2011
Figure 5. Regulated Dual Supply
Operation With a Load Common to a Voltage of Opposite Polarity
In many cases, a regulator powers a load that is not connected to ground, but instead, is connected to a voltage
source of opposite polarity (for example, operational amplifiers, level-shifting circuits, and so on). In these cases,
a clamp diode should be connected to the regulator output as shown in Figure 6. This protects the regulator from
output polarity reversals during startup and short-circuit operation.
Figure 6. Output Polarity-Reversal-Protection Circuit
Reverse-Bias Protection
Occasionally, the input voltage to the regulator can collapse faster than the output voltage. This can occur, for
example, when the input supply is crowbarred during an output overvoltage condition. If the output voltage is
greater than approximately 7 V, the emitter-base junction of the series-pass element (internal or external) could
break down and be damaged. To prevent this, a diode shunt can be employed as shown in Figure 7.
Figure 7. Reverse-Bias-Protection Circuit
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