LTC1052/LTC7652
W U U
U
APPLICATIO S I FOR ATIO
OUTPUT CLAMP
within approximately 1V of either supply rail. This switch
is in parallel with the amplifier’s feedback resistor. As the
output moves closer to the rail, the switch on
resistance decreases, reducing the closed loop gain. The
output swing is reduced when the clamp function is used.
If the LTC1052 is driven into saturation, the nulling loop,
attempting to force the differential input voltage to zero,
will drive CEXTA and CEXTB to a supply rail. After the
saturating drive is removed, the capacitors take a finite
time to recover—this is the overload recovery time. The
overload recovery is longest when the capacitors are
driven to the negative rail (refer to Overload Recovery in
the Typical Performance Characteristics section). The
overload recovery time in this case is typically 225ms. In
the opposite direction (i.e., CEXTA and CEXTB at positive
rail), it is about ten times faster (25ms). The overload
recovery time for the LTC1052 is much faster than com-
petitive devices; however, if a faster overload recovery
time is necessary, the output clamp function can be used.
How much current the output clamp leaks when off
is important because, when used, it is connected to the
amplifier’s negative input. Any current acts like input bias
current and will degrade accuracy. At the other extreme,
the maximum current the clamp conducts when on deter-
mines how much overdrive the clamp will take, and still
keep the amplifier from saturating. Both of these numbers
are guaranteed in the Electrical Characteristics section.
LOW SUPPLY OPERATION
The minimum supply voltage for proper operation of the
LTC1052 is typically 4.0V (±2.0V). In single supply
applications, PSRR is guaranteed down to 4.7V (±2.35V).
This assures proper operation down to the minimum TTL
specified voltage of 4.75V.
When the output clamp is connected to the negative input
it prevents the amplifier from saturating, thus keeping
CEXTA and CEXTB at their nominal voltages. The output
clamp is a switch that turns on when the output gets to
U
TYPICAL APPLICATIO S
5V Powered Ultraprecision Instrumentation Amplifier
Fast Precision Inverter
5V
5V
10k*
10k*
8pF
4
INPUT
3
2
7
+ IN
7
8
+
6
10k
V
LTC1052
OUT
8
–
11
12
1
1N4148
4
C1
C2
0.1µF
1µF
1µF
0.1µF
R2
100k
1000pF
300pF
R1
100
5V
2
3
13
6
7
– IN
5V
14
5
5V
7
+
–
6
2
3
LTC1043
0.22µF
+
OUTPUT
LT318A
6
LTC1052
4
10k
43k
8
10k
–
4
–5V
1
+
2
C4
1µF
10k
0.1µF
0.1µF
C3
1µF
1N914
3
– 5V
*1% METAL FILM
FULL POWER BANDWIDTH = 2MHz
≈ – 0.5V
18
17
15
16
SLEW RATE = 40V/µs
SETTLING (10V STEP) = 12µs TO 0.01%
BIAS CURRENT DC = 30pA
OFFSET DRIFT = 50nV/°C
0.0047µF
CIRCUITRY WITHIN DASHED LINES MAY BE DELETED IF OUTPUT
DOES NOT HAVE TO SWING ALL THE WAY TO GROUND
DRIFT = 50nV/°C
OFFSET VOLTAGE = 5µV
LTC1052/7652 • TA04
V
= 3µV
OS
R2
GAIN =
+ 1
R1
CMRR = >120dB DC – 20kHz
BANDWIDTH = 10Hz
LTC1052/7652 • TA03
1052fa
12
Linear [ Linear ]
