Application Information

General

The LM6118/LM6218 are high-speed, fast-settling dual

op-amps. To insure maximum performance, circuit board lay-

out is very important. Minimizing stray capacitance at the in-

puts and reducing coupling between the amplifier’s input and

output will minimize problems.

Supply Bypassing

To assure stability, it is recommended that each power sup-

ply pin be bypassed with a 0.1 µF low inductance capacitor

near the device. If high frequency spikes from digital circuits

or switching supplies are present, additional filtering is rec-

ommended. To prevent these spikes from appearing at the

output, R-C filtering of the supplies near the device may be

necessary.

Power Dissipation

These amplifiers are specified to 20 mA output current. If ac-

companied with high supply voltages, relatively high power

dissipation in the device will occur, resulting in high junction

temperatures. In these cases the package thermal resis-

tance must be taken into consideration. (See Note 5 under

Electrical Characteristics.) For high dissipation, an N pack-

age with large areas of copper on the pc board is recom-

mended.

Amplifier Shut Down

If one of the amplifiers is not used, it can be shut down by

connecting both the inverting and non-inverting inputs to the

V− pin. This will reduce the power supply current by approxi-

mately 25%.

Capacitive Loading

Maximum capacitive loading is about 50 pF for a closed-loop

gain of +1, before the amplifier exhibits excessive ringing

and becomes unstable. A curve showing maximum capaci-

tive loads, with different closed-loop gains, is shown in the

Typical Performance Characteristics section.

To drive larger capacitive loads at low closed-loop gains, iso-

late the amplifier output from the capacitive load with 50

Ω.

Connect a small capacitor directly from the amplifier output

to the inverting input. The feedback loop is closed from the

isolated output with a series resistor to the inverting input.

Amplifier to Amplifier Coupling

DS010254-23

DS010254-7

DS010254-8

DS010254-9

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