LT1815 LINER [Linear Technology], LT1815 Datasheet - Page 13

• Manufacturer Part Number: LT1815
• Description: Single/Dual/Quad 220MHz, 1500V/us Operational Amplifiers with Programmable Supply Current
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
Figure 2. Gain Bandwidth Product vs R
Figure 3. Supply Current vs R
Figure 1. Programming Resistor Between I
250
200
150
100
50
0
7
6
5
4
3
2
1
0
10
10
R
R
SET
SET
U
PROGRAMMING RESISTOR ( )
100
PROGRAMING RESISTOR ( )
100
–
+
LT1815S6
R
I
SET
R
L
U
SET
= 100
5V
1k
1k
V
V
SET
+
–
181567 F01
V
T
PER AMPLIFIER
Programming Resistor
R
A
S
SET
L
= 5V
= 25 C
W
= 500
V
T
10k
S
A
Programming Resistor
10k
–5V
= 5V
= 25 C
181567 F02
181567 F03
40k
40k
SET
and V
U
–
Power Dissipation
The LT1815/LT1816/LT1817 combine high speed and
large output drive in small packages. It is possible to
exceed the maximum junction temperature specification
(150 C) under certain conditions. Maximum junction tem-
perature (T
(T
amplifiers (n) as follows:
Power dissipation is composed of two parts. The first is
due to the quiescent supply current and the second is due
to on-chip dissipation caused by the load current. The worst-
case load induced power occurs when the output voltage
is at 1/2 of either supply voltage (or the maximum swing
if less than 1/2 the supply voltage). Therefore P
Example: LT1816IS8 at 85 C, V
Circuit Operation
The LT1815/LT1816/LT1817 circuit topology is a true
voltage feedback amplifier that has the slewing behavior of
a current feedback amplifier. The operation of the circuit
can be understood by referring to the Simplified Sche-
matic. Complementary NPN and PNP emitter followers
buffer the inputs and drive an internal resistor. The input
voltage appears across the resistor, generating current
that is mirrored into the high impedance node.
Complementary followers form an output stage that buff-
ers the gain node from the load. The input resistor, input
stage transconductance and the capacitor on the high
impedance node determine the bandwidth. The slew rate
is determined by the current available to charge the gain
node capacitance. This current is the differential input
voltage divided by R1, so the slew rate is proportional to
the input step. Highest slew rates are therefore seen in the
lowest gain configurations.
A
T
P
P
P
T
), power dissipation per amplifier (P
J
JMAX
DMAX
DMAX
DMAX
= T
A
= 85 C + (2 • 178mW) • (150 C/W) = 138 C
= (V
= (V
= (10V) • (11.5mA) + (2.5V)
+ (n • P
J
) is calculated from the ambient temperature
(V
+
+
OMAX
– V
– V
D
–
–
/R
•
) • (I
) • (I
L
)
JA
)
SMAX
SMAX
) + (V
) + (V
LT1816/LT1817
S
= 5V, R
+
+
/2)
– V
2
D
/100 = 178mW
2
) and number of
/R
OMAX
L
L
=100
LT1815
or
) •
DMAX
13
181567fa
is: