LT1166 Linear Technology, LT1166 Datasheet - Page 10

• Manufacturer Part Number: LT1166
• Description: Power Output Stage Automatic Bias System
• Manufacturer: Linear Technology

APPLICATIONS
LT1166
1A Adjustable Voltage Reference
The circuit in Figure 12 uses the LT1166 in a feedback loop
with the LT1431 to make a voltage reference with an
“attitude.” This 5V reference can drive 1A and maintain
0.4% tolerance at the output. If other output voltages are
desired, external resistors can be used instead of the
LT1431’s internal 5k resistors.
HIGH VOLTAGE APPLICATION CIRCUITS
In order to use op amps in high voltage applications it is
necessary to use techniques that confine the amplifier’s
10
U
R
4
5k
5k
TOP
INFORMATION
7
R
5
U
MID
GND/SENSE
2.5V
8
REF
+
–
–
W
Figure 13. Op Amp in Suspended-Supply Operation
LT1431
V
3
+
Figure 12. 1A, 5V Voltage Reference
IN
U
1
COL
GND
FORCE
6
1k
9.1k
10k
R7
R9
12V
2k
12V
2
–
+
100
V
IN
R10
common mode voltage to its output. The following appli-
cations utilize amplifiers operating in suspended-supply
operation (Figure 13). See “Linear Technology Magazine”
Volume IV Number 2 for a discussion of suspended
supplies. The gain setting resistors used in suspended-
supply operation must be tight tolerance or the gain will be
wrong. For example: with 1% resistors the gain can be as
far off as 75%, but with 0.1% resistors that error is cut to
less than 5%. Using the values shown in Figure 13, the
formula for computing the gain is:
R8
V
1k
1k
LT1166
BOTTOM
V
TOP
A
1
4
V
100
SENSE
SENSE
1166 • F13
=
I
V
I
LIM
LIM
(R8 • R9) – (R7 • R10)
OUT
+
+
–
–
100
100
OUT
8
7
3
6
5
R8(R9 + R10)
1 F
1 F
1k
1k
12V
IRF9530
1
1
IRF530
+
220 F
1166 • F12
= –11.22
5V
OUT