ELH0101 데이터 시트보기 (PDF) - Elantec -> Intersil

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ELH0101

Power Operational Amplifier

Elantec -> Intersil 

ELH0101 883 8508901 2YX

Power Operational Amplifier

Application Information Contd

Cooling is normally required to maintain the

worst case operating junction temperature TJ of

the device below the specified maximum value

TJ(MAX) TJ can be calculated from known oper-

ating conditions Rewriting equation (1) we find

iJA

e

TJ

b TA

PD

C

W

TJ e TA a PDiJA C

l Where PD e (VS b VOUT) IOUT a Vg

(Vb)lIQ

iJA e iJC a iCS a iSA and

VS e Supply Voltage

iJC for the ELH0101 is typically 2 C W

Stability and Compensation

As with most amplifiers care should be taken

with lead dress component placement and sup-

ply decoupling in order to ensure stability For

example resistors from the output to an input

should be placed with the body close to the input

to minimize ‘‘pickup’’ and maximize the frequen-

cy of the feedback pole by minimizing the capaci-

tance from the input to ground

A feedback pole is created when the feedback

around any amplifier is resistive The parallel re-

sistance and capacitance from the input of the

device (usually the inverting input) to AC

ground set the frequency of the pole In many

instances the frequency of this pole is much

greater than the expected 3 dB frequency of the

closed loop gain and consequently there is negli-

gible effect on stability margin However if the

feedback pole is less than approximately six

times the expected 3 dB frequency a lead capaci-

tor should be placed from the output to the input

of the op amp The value of the added capacitor

should be such that the RC time constant of this

capacitor and the resistance it parallels is greater

than or equal to the original feedback pole time

constant

Some inductive loads may cause output stage os-

cillation A 0 01 mF ceramic capacitor in series

with a 10X resistor from the output to ground

will usually remedy this situation

0101 – 16

Capacitive loads may be compensated for by tra-

ditional techniques (See ‘‘Operational Amplifi-

ers Theory and Practice’’ by Roberge published

by Wiley )

0101 – 17

A similar but alternative technique may be used

for the ELH0101

0101 – 18

11

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