LT1499CS(RevE) View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LT1499CS
(Rev.:RevE)
(Rev.:RevE)
Linear Technology
LT1499CS Datasheet PDF : 20 Pages
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APPLICATIONS INFORMATION
without oscillation at unity gain. When driving a heavy
capacitive load, the bandwidth is reduced to maintain
stability. Figures 2a and 2b illustrate the stability of the
device for small-signal and large-signal conditions with
capacitive loads. Both the small-signal and large-signal
transient response with a 10nF capacitive load are well
behaved.
Feedback Components
To minimize the loading effect of feedback, it is possible
to use the high value feedback resistors to set the gain.
However, care must be taken to insure that the pole formed
by the feedback resistors and the total input capacitance
at the inverting input does not degrade the stability of the
amplifier. For instance, the LT1498/LT1499 in a noninvert-
ing gain of 2, set with two 30k resistors, will probably
oscillate with 10pF total input capacitance (5pF input
capacitance + 5pF board capacitance). The amplifier has
a 2.5MHz crossing frequency and a 60° phase margin at
6dB of gain. The feedback resistors and the total input
capacitance create a pole at 1.06MHz that induces 67° of
phase shift at 2.5MHz! The solution is simple, either lower
the value of the resistors or add a feedback capacitor of
10pF of more.
LT1498/LT1499
CL = 0pF
CL = 500pF
CL = 10nF
VS = 5V
AV = 1
14989 F02a
Figure 2a. LT1498 Small-Signal Response
CL = 0pF
CL = 500pF
CL = 10nF
VS = 5V
AV = 1
14989 F02b
Figure 2b. LT1498 Large-Signal Response
TYPICAL APPLICATIONS
1A Voltage Controlled Current Source
0.5Ω
V+
1k
–
1/2 LT1498
1k
VIN
+
500pF
100Ω
Si9430DY
IOUT
=
V+ – VIN
0.5Ω
tr < 1μs
IOUT
RL
14989 TA03
1A Voltage Controlled Current Sink
V+
1k
VIN
+
1/2 LT1498
–
V+
IOUT
100Ω
RL
Si9410DY
500pF
1k
IOUT
=
VIN
0.5Ω
tr < 1μs
0.5Ω
14989 TA04
14989fe
15
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