LT1207 데이터 시트보기 (PDF) - Linear Technology
부품명
상세내역
제조사
LT1207 Datasheet PDF : 16 Pages
| |||
LT1207
APPLICATI S I FOR ATIO
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.
RF = 750Ω
RL = 50Ω
LT1207 • F05c
Figure 5c. Large-Signal Response, AV = 2
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 CL = 10,000pF. The slew
rate is about 60V/µs, determined by the current limit of
600mA.
VS = ±15V
RF = RG = 3k
RL = ∞
LT1207 • F06
Figure 6. Large-Signal Response, CL = 10,000pF
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.
Power Supplies
The LT1207 will operate from single or split supplies from
±5V (10V total) to ±15V (30V total). It is not necessary to
use equal value split supplies, however the offset voltage
and inverting input bias current will change. The offset
voltage changes about 500µV per volt of supply mis-
match. The inverting bias current can change as much as
5µA per volt of supply mismatch, though typically the
change is less than 0.5µA per volt.
Thermal Considerations
Each amplifier in the LT1207 includes a separate thermal
shutdown circuit which protects against excessive inter-
nal (junction) temperature. If the junction temperature
exceeds the protection threshold, the amplifier will begin
cycling between normal operation and an off state. The
cycling is not harmful to the part. The thermal cycling
occurs at a slow rate, typically 10ms to several seconds,
which depends on the power dissipation and the thermal
time constants of the package and heat sinking. Raising
the ambient temperature until the device begins thermal
shutdown gives a good indication of how much margin
there is in the thermal design.
Heat flows away from the amplifier through the package’s
copper lead frame. Heat sinking is accomplished by using
the heat spreading capabilities of the PC board and its
copper traces. Experiments have shown that the heat
spreading copper layer does not need to be electrically
connected to the tab of the device. The PCB material can
be very effective at transmitting heat between the pad area
attached to the tab of the device and a ground or power
plane layer either inside or on the opposite side of the
board. Although the actual thermal resistance of the PCB
material is high, the length/area ratio of the thermal
11
Share Link: 