Datasheet

10
LT1210
1210fa
U
S
A
O
PP
L
IC
AT
I
WU
U
I FOR ATIO
When the LT1210 is used to drive capacitive loads, the
available output current can limit the overall slew rate. In
the fastest configuration, the LT1210 is capable of a slew
rate of over 1V/ns. The current required to slew a capacitor
at this rate is 1mA per picofarad of capacitance, so
10,000pF would require 10A! The photo (Figure 6) shows
the large-signal behavior with C
L
= 10,000pF. The slew
rate is about 150V/µs, determined by the current limit of
1.5A.
the bandwidth is reduced. The photos in Figures 5a, 5b and
5c show the large-signal response of the LT1210 for
various gain configurations. The slew rate varies from
770V/µs for a gain of 1, to 1100V/µs for a gain of –1.
1210 F05c
R
F
= R
G
= 750Ω
R
L
= 10Ω
Figure 5c. Large-Signal Response, A
V
= 2
Figure 5a. Large-Signal Response, A
V
= 1
1210 F05a
R
F
= 825Ω
R
L
= 10Ω
V
S
= ±15V
R
F
= R
G
= 750Ω
R
L
= 10Ω
V
S
= ±15V
1210 F05b
1210 F06
R
F
= R
G
= 3k
R
L
= ∞
V
S
= ±15V
Differential Input Signal Swing
The differential input swing is limited to about ±6V by an
ESD protection device connected between the inputs. In
normal operation, the differential voltage between the
input pins is small, so this clamp has no effect; however,
in the shutdown mode the differential swing can be the
same as the input swing. The clamp voltage will then set
the maximum allowable input voltage. To allow for some
margin, it is recommended that the input signal be less
than ±5V when the device is shut down.
Capacitance on the Inverting Input
Current feedback amplifiers require resistive feedback
from the output to the inverting input for stable operation.
Take care to minimize the stray capacitance between the
output and the inverting input. Capacitance on the invert-
ing input to ground will cause peaking in the frequency
response (and overshoot in the transient response), but it
does not degrade the stability of the amplifier.
Figure 5b. Large-Signal Response, A
V
= –1
Figure 6. Large-Signal Response, C
L
= 10,000pF
V
S
= ±15V