Datasheet

µA78xx
+V
O
+V
I
−V
O
1N4001
or
Equivalent
µA7815C
0.1 µF
1N4001
0.1 µF
1N4001
0.33 µF
2 µF
1N4001
1N4001
V
O
= 15 V
V
O
= −15 V
20-V Input
−20-V Input
µA7915C
1 µF
V
O(Reg)
R1
Input
I
O
I
O
= (V
O
/R1) + I
O
Bias Current
0.33 µF
µA78xx
Output
μA7800 SERIES
www.ti.com SLVS056O –MAY 1976–REVISED AUGUST 2012
Figure 5. Current Regulator
Figure 6. 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 (e.g., operational amplifiers, level-shifting circuits, etc.). In these cases, a clamp diode
should be connected to the regulator output as shown in Figure 7. This protects the regulator from output polarity
reversals during startup and short-circuit operation.
Figure 7. 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 used as shown in Figure 8.
Copyright © 1976–2012, Texas Instruments Incorporated Submit Documentation Feedback 9