EL2003 데이터 시트보기 (PDF) - Intersil
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EL2003 Datasheet PDF : 12 Pages
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DIRECT DRIVE
EL2003, EL2033
The easiest way to drive capacitive loads is to isolate them
from the feedback with a series resistor. Ten to twenty ohms
is usually enough but the final value depends on the op amp
used and the range of load capacitance.
DOUBLE MATCHED
BACK MATCHED
Op Amp Booster
The EL2003 or EL2033 can boost the output drive of almost
any monolithic op amp. Because the phase shift in the
EL2003 and EL2033 is low at the op amp's unity gain
frequency, no additional compensation is required. By
following an op amp with an EL2003 or EL2033, the buffered
op amp can drive cables and other low impedance loads
directly. Even decompensated high speed op amps can take
advantage of the EL2003’s or EL2033’s 100mA drive.
10Ω is enough isolation and speed is
determined by the isolation resistor and
capacitive load time constant.
OP AMP BOOSTER WITH CAPACITIVE LOAD
CL
10pF
tR
17ns
OS
10%
470pF
20ns
50%
0.001µF
30ns
35%
0.005µF
80ns
0
0.01µF
220ns
0
0.05µF
1.1µs
0
0.1µF
2.2µs
0
If the system requirements will not tolerate the isolation
resistor, then additional high frequency feedback from the op
amp output (the buffer input) and an isolating resistor from
the buffer output is required. This requires that the op amp
be unity gain stable.
OP AMP BOOSTER
Driving capacitive loads with any closed loop amplifier
creates special problems. The open loop output impedance
works into the load capacitance to generate phase lag which
can make the loop unstable. The output impedance of the
EL2003 or EL2033 is less than 10Ω from DC to about
10MHz, but a capacitive load of 1000pF will generate about
45° phase shift at 10MHz and make high speed op amps
unstable. Obviously more capacitance will cause the same
problem but at lower frequencies, and slower op amps as
well would become unstable.
This works with any unity gain stable OA.
Snubber Circuit (51Ω 470pF) is optional.
COMPLEX FEEDBACK WITH THE BUFFER TO DRIVE
CAPACITIVE LOADS
8
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