LM321

SNOS935C – FEBRUARY 2001 – REVISED DECEMBER 2014

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Typical Applications (continued)

8.2.4 Power Amplifier

Power amplifier application circuit is shown in Figure 11. Voltage gain is set by R1 and R2. The output of the

amplifier is connected to the base of BJT which amplifies the current. Current gain is set by

β, current gain of a

BJT. The resulting output provides high power to the load. Differential voltage supplies are necessary.

V0 = 0 VDC for VIN = 0 VDC, AV = 10

Figure 11. Power Amplifier Schematic

8.2.5 LED Driver

LM321 operating as an LED driver is shown in Figure 12. The output of the amplifier sets the current through the

diode. The voltage across the LED is assumed constant.

Figure 12. LED Driver Schematic

8.2.6 Fixed Current Sources

Operational amplifier can be used to provide fixed current source to multiple loads. The output voltage of the

amplifier is connected to bases of bipolar transistors. The feedback is provided from the drain of a BJT to the

inverting terminal of the amplifier. Currents in the second and later BJTs are set by the ratio of R1 and R2.

Figure 13. Fixed Current Sources Schematic

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