LM6162 datasheet(7/12 Pages) NSC

7 / 12 page

Application Tips

The LM6362 has been decompensated for a wider gain-

bandwidth product than the LM6361 However the LM6362

still offers stability at gains of 2 (and b1) or greater over the

specified ranges of temperature power supply voltage and

load Since this decompensation involved reducing the emit-

ter-degeneration resistors in the op amp’s input stage the

DC precision has been increased in the form of lower offset

voltage and higher open-loop gain

Other op amps in this family include the LM6361 LM6364

and LM6365 If unity-gain stability is required the LM6361

should be used The LM6364 has been decompensated for

operation at gains of 5 or more with corresponding greater

gain-bandwidth product (125 MHz typical) and DC preci-

sion The fully-uncompensated LM6365 offers gain-band-

width product of 725 MHz typical and is stable for gains of

25 or more All parts in this family regardless of compensa-

tion have the same high slew rate of 300 V ms (typ)

The LM6362 is unusually tolerant of capacitive loads Most

op amps tend to oscillate when their load capacitance is

greater than about 200 pF (in low-gain circuits) However

load capacitance on the LM6362 effectively increases its

compensation capacitance thus slowing the op amp’s re-

sponse and reducing its bandwidth The compensation is

not ideal though and ringing may occur in low-gain circuits

with large capacitive loads

Power supply bypassing is not as critical for LM6362 as it is

for other op amps in its speed class However bypassing

will improve the stability and transient response of the

LM6362 and is recommended for every design 001 mFto

01 mF ceramic capacitors should be used (from each sup-

ply ‘‘rail’’ to ground) if the device is far away from its power

supply source an additional 22 mFto10 mF of tantalum

may be required for extra noise reduction

Keep all leads short to reduce stray capacitance and lead

inductance and make sure ground paths are low-imped-

ance especially where heavier currents will be flowing

Stray capacitance in the circuit layout can cause signal cou-

pling from one pin input or lead to another and can cause

circuit gain to unintentionally vary with frequency

Breadboarded circuits will work best if they are built using

generic PC boards with a good ground plane If the op amps

are used with sockets as opposed to being soldered into

the circuit the additional input capacitance may degrade

circuit frequency response At low gains (a2or b1) a

feedback capacitor Cf from output to inverting input will

compensate for the phase lag caused by capacitance at the

inverting input Typically values from 2 pF to 5 pF work well

however best results can be obtained by observing the am-

plifier pulse response and optimizing Cf for the particular

layout

Typical Applications

Offset Voltage Adjustment

TLH11061 11

Inverting Amplifier 30 MHz Bandwidth

Operation

15V

supplies results in wider

bandwidth

MHz

(typ)

TLH11061 12

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