!5 '-'
....
~ 13 -5
~ ~ -10
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en:.:
en -15
t:--
j..----55'C 25'C 125'C Vs ~ ± 15V 125'C 25'C
55'C
"
~ 0.1 SLEW~ w
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so ~ 0.01 Vs - + 15V en TA - 25'C
11111
GBW
I ....
w '-' ~
w
"-;;!!
....
100 I--+-+---:;;;;¥==i==i
~ 0.1 ~----t---+---oI'9--jr----j
=>
o 0.01
-20 V 0.001 II111111 1
o 1 1 10 100 1000 10,000 10 100 lk 10k lOOk
TIME FROM OUTPUT SHORT (MINUTES) OVER-COMPENSATION CAPACITOR (pF) FREQUENCY (Hz)
APPLICATions InFoRmATion
The LT1012 may be inserted directly into OP-07, LM11, 108A or 101A sockets with or without removal of external frequency compensation or nulling compo-nents. The LT1012 can also be used in 741, LF411, LF156 or OP-15 applications provided that the nulling circuitry is removed.
The L T1012 is specified over a wide range of power supply voltages from ± 2V to ± 18V. Operation with lower supplies is possible down to ± 1.0V (two Ni-Cad batteries) .
Achieving Picoampere/Microvoll Performance
In order to realize the picoampere - microvolt level accuracy of the LT1012, proper care must be exer-cised. For example, leakage currents in circuitry
exter-nal to the op amp can Significantly degrade performance. High quality insulation should be used (e.g. Teflon, Kel-F); cleaning of all insulating surfaces to remove fluxes and other residues will probably be required. Surface coating may be necessary to pro-vide a moisture barrier in high humidity environments.
OFFSET TRIM
v+
I~
OUTPUT,
~7
8I'
OVERCOMP 0 ~4 5
~~
3 ... " ,
~ ~i'
v-GUARD
APPLICATions InFoRmATion
Board leakage can be minimized by encircling the in-put circuitry with a guard ring operated at a potential close to that of the inputs: in inverting configurations the guard ring should be tied to ground, in non-invert-ing connections to the invertnon-invert-ing input at pin 2. Guard-ing both sides of the printed circuit board is required.
Bulk leakage reduction depends on the guard ring width. Nanoampere level leakage into the offset trim terminals can affect offset voltage and drift with temperature.
Microvolt level error voltages can also be generated in the external circuitry. Thermocouple effects caused by temperature gradients across dissimilar metals at the contacts to the input terminals can exceed the inher-ent drift of the amplifier. Air currinher-ents over device leads should be minimized, package leads should be short, and the two input leads should be as close together as possible and maintained at the same temperature.
Noise Testing
For application information on noise testing and cal-culations, please see the LT1008 data sheet.
Frequency Compensation
The LT1012 can be overcompensated to improve ca-pacitive load handling capability or to narrow noise bandwidth. In many applications, the feedback loop around the amplifier has gain (e.g. logarithmic amplifi-ers); overcompensation can stabilize these circuits with a single capacitor.
The availability of the compensation terminal permits the use of feedforward frequency compensation to en-hance slew rate. The voltage follower feedforward scheme bypasses the amplifier's gain stages and slews at nearly 10V / J,Lsec.
The inputs of the LT1012 are protected with back-to-back diodes. Current limiting resistors are not used, because the leakage of these resistors would prevent the realization of picoampere level bias currents at ele-vated temperatures. In the voltage follower
configura-'"
CICtion, when the input is driven by a fast, large signal ~ pulse (> 1V), the input protection diodes effectively
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. Jshort the output to the input during slewing, and a cur- Q.
rent, limited only by the output short circuit protection
e
will flow through the diodes.
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The use of a feedback resistor, as shown in the voltage follower feedforward diagram, is recommended be-cause this resistor keeps the current below the short circuit limit, resulting in faster recovery and settling of the output.
Test Circuit for Offset Voltage and its Drill with Temperature
R2 1000
R3 50k
R1
·50k + 15V
-15V Va ~ 1000 Vas
> , - - - 4 - - -Va
• RESISTORS MUST HAVE LOW THERMOELECTRIC POTENTIAL
• • THIS CIRCUIT IS ALSO USED AS THE BURN·IN CONFIGURATION FOR THE LT1012. WITH SUPPLY VOLTAGES INCREASED TO :20V. R1 =R3=20k.
R2 = 2000. Av= 100.
Follower Feedforward Compensation
50pF
;;:J!l~,.::....j~OUTPUT INPUT --"N"-___ ""i
5k
Pulse Response of Feedforward Compensation
a::
Co ;:
a:::
CIC
~
o
TYPICAL APPLICATions
Resistor Multiplier
R,"=:..-_-.-...::.
lG!!
R, 10M
R2 lk
R3 lOOk
Instrumentation Amplifier with ± 100 Vall Common Mode Range
10M 10011
100M INPUT
100M + - - - " M -... ....:.
REFERENCE IN 0.1V to tOV
10M -15V All Resistors 1% or better
+ R, lk
Air Flow Detector
I I COLO JUNCTION AT AMBIENT Mount R, in airflow.
+15V
-15V
OUTPUT INPUT
1000V 10k
"No Trims" 12 bit Multiplying DAC Output Amplifier
r-_ _ _ _ ...L...;R',EEDBACK
/ / /
12 bit CMOS MULTIPLYING
DAC
When the reference input drops to O.lV. the least significant bit decreases to the microvoltlpicoampere range.
Low Power Comparator with < lOIN Hysteresis
I I /
-5V
Input Amplifier for 4% Digit Voltmeter
, - - - 7
/ I
I I
/ I
I I
/ +15V I
lOOk 5%
• RATIO MATCH ± .01%
/
TO lV FULL SCALE ANALOG TO DIGITAL CONVERTER
FN507 This application requires low bias current and offset voltage. low noise. and low drift with time and temperature.
ALLEN BRADLEY DECADE VOLTAGE DIVIDER
TYPICAL APPLICATions
alA
+15V 10k'
INPUT -""",'-"-""i
+
15.7k*
OUTPUT
-= + TEL. LABS, TYPE 081
* 1% FILM RESISTOR 01 2N2979
Saturated Standard Cell Amplifier
>= __ - OUTPUT
1.018235V -15V
SATURATED STANDARD CELL
#101 R2
EPPLEY LABS Rl
NEWPORT, R.I.
The typical 30pA bias current of the LT1012 will degrade the standard cell by only 1 ppm/year. Noise is a fraction of a ppm. Unprotected gate MOSFET isolates standard cell on power down.
Amplifier For Photodiode Sensor
Rl 5M 1%
OUTPUT
Logarithmic Amplifier
lk+
alB 124k * 5.1k
~--<p---t---'lN.--... -"NI.--+15V
-=
Rl lOOk
LT·l004 1.2V
Low bias current and offset voltage of the LT1012 allow 4'12 decades of voltage input logging.
Amplifier for Bridge Transducers
~--_v+
R3 510k
R4 510k R2
lOOk R6
56M R5 56M
VOLTAGE GAIN
~ 100
Buffered Reference for A to D Converters
+15--~~P---~---,
7k 200
.... ---"'V\i"r---+-3k OUTPUT 10V Ik
* THE I K PRELOAD lk MINIMIZES GLITCHES
-=-INDUCED BY TRANSIENT LOADS
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HI
TYPICAL APPLICATions
1Hz to 1MHz Voltage to Frequency Converter
1.8k
+15V--~~-,---,
5k
INPUT 22.1k
o to 10V (metal film)
10k
+15V
10k 299k
1684 LTt004
-1.2 186
+ YSI #44007 COLD JUNCTION COMPENSATION ± 1 'C OVER 0 to 60'C
lk
1000pF
Thermocouple Thermometer
3.8k 1M
1.8k
1.8k
-15V
lOOk
200k
-15V
!1Il!>'--... -OUTPUT 10mV/'C
r - - . - - + 15V
10pF
All diodes: lN4148
The LT1012 provides DC stabilization for the 356 integrator, allowing 120dB dynamic range. No offset trim is required.
1.8k
Charge Amplifier for Piezoelectric Transducers
10k
10k
Fast Precision Inverters
10k' INPUT
-15V 1N4148 (4)
300pF
10k
INPUT 10k'
SLEW RATE @ 100V I"S 10k
300pF +15V
10k SETILING ~ 5~S TO .01%/10 VOLT STEP
OFFSET VOLTAGE ~ 30~V
-15V BIAS CURRENT ~ 30pA
*1% METAL FILM
Ammeter With Six Decade Range
10k
--~"""'~~'"I CURRENT INPUT
01,02,03,04, RCA CA3146 TRANSISTOR ARRAY.
CALIBRATION: ADJUST R1 FOR FULL SCALE DEFLECTION WITH 1~A INPUT CURRENT.
Ammeter measures currents from 100pA to 100~A
without the use of expensive high value resistors. Ac-curacy at 100~A is limited by the offset voltage be-tween 01 and 02 and. at 100pA. by the inverting bias
10k'
10pF 1N4148
+15V
10k -15V
'1% METAL FILM FULL POWER BANDWIDTH ~ 2MHz SLEW RATE ~ 50V 1 "sec
SETTLING (10V STEP) ~ 12"S TO 0,01%
BIAS CURRENT DC ~ 30pA OFFSET DRIFT ~ 0.3"V 1°C OFFSET VOLTAGE ~ 30" V
,...--_-_--_9_-"""""-10k +15V
R1 2k
1.2k
LT1004C
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