LT1722 LINER [Linear Technology], LT1722 Datasheet - Page 13

• Manufacturer Part Number: LT1722
• Description: Single, Dual, Quad 200MHz Low Noise Precision Op Amps
• Manufacturer: LINER [Linear Technology]

SI PLIFIED SCHE ATIC
APPLICATIO S I FOR ATIO
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.
Worst-case instantaneous power dissipation for a given
resistive load in one amplifier occurs at the maximum
supply current and when the output voltage is at half of
either supply voltage (or the maximum swing if less than
half supply voltage).
Therefore P
Example. Worst-case conditions are: both op amps in the
LT1723IS8 are at T
V
which is less than the absolute maximum rating at 150 C.
OUT
W
P
or
P
P
T
J(MAX)
D(MAX)
D(MAX)
D(MAX)
= 2.5V.
= 2 •[(10V)(5.95mA) + (2.5V)
= 85 C + (203mW)(190 C/W) = 124 C
= (V
= (V
D(MAX)
(V
+IN
+
+
+
– V
– V
– V
in one amplifier is:
U
A
–
–
O(MAX)
)(I
)(I
= 85 C, V
Q1
R1
S(MAX)
S(MAX)
I
1
U
W
)(V
D1
D2
R
O(MAX)
) + (V
) +
S
W
= 5V, R
+
Q2
/R
/2)
2
L
/150 ] = 203mW
R2
2
)
I
2
/R
L
–IN
L
U
Q3
Q5
= 150 ,
Circuit Operation
The LT1722/LT1723/LT1724 circuit topology is a voltage
feedback amplifier. The operation of the circuit can be
understood by referring to the Simplified Schematic. The
first stage is a folded cascode formed by the transistors
Q1 through Q4. A degeneration resistor, R, is used in the
input stage. The current mirror Q5, Q6 is bootstrapped by
Q7. The capacitor, C, assures the bandwidth and the slew
rate performance. The output stage is formed by comple-
mentary emitter followers, Q8 through Q11. The diodes
D1 and D2 protect against input reversed biasing. The
remaining part of the circuit assures optimum voltage and
current biases for all stages.
Low noise, reduced current supply, high speed and DC
accurate parameters are distinctive features of the LT1722/
LT1723/LT1724.
Q6
Q4
I
3
V
C
BIAS
Q7
LT1722/LT1723/LT1724
Q8
I
5
Q9
I
4
Q10
Q11
1723 SS
V
OUT
V
S
S
+
–
13
172234fa