AMP01AX Analog Devices Inc, AMP01AX Datasheet - Page 11

• Manufacturer Part Number: AMP01AX
• Description: Instrumentation Amplifier IC
• Manufacturer: Analog Devices Inc

Specifications of AMP01AX

• Gain Max, V/v: 10000
• Input Offset Voltage Max: 50V
• Supply Voltage Max: 18V
• Mounting Type: Through Hole
• Supply Voltage Min: 4.5V
• Gain Min, V/v: 0.1
• Package / Case: 18-CDIP
• Rohs Status: RoHS non-compliant
• Amplifier Type: Instrumentation
• Number Of Circuits: 1
• Slew Rate: 4.5 V/µs
• -3db Bandwidth: 570kHz
• Current - Input Bias: 1nA
• Voltage - Input Offset: 20µV
• Current - Supply: 3mA
• Current - Output / Channel: 120mA
• Voltage - Supply, Single/dual (±): ±4.5 V ~ 18 V
• Operating Temperature: -55°C ~ 125°C
• Output Type: -
• Gain Bandwidth Product: -

INPUT AND OUTPUT OFFSET VOLTAGES
Instrumentation amplifiers have independent offset voltages
associated with the input and output stages. While the initial
offsets may be adjusted to zero, temperature variations will
cause shifts in offsets. Systems with auto-zero can correct for
offset errors, so initial adjustment would be unnecessary. How-
ever, many high-gain applications don’t have auto zero. For
these applications, both offsets can be nulled, which has mini-
mal effect on TCV
The input offset component is directly multiplied by the ampli-
fier gain, whereas output offset is independent of gain. There-
fore, at low gain, output-offset errors dominate, while at high
gain, input-offset errors dominate. Overall offset voltage, V
referred to the output (RTO) is calculated as follows;
where V
specifications and G is the amplifier gain. Input offset nulling
alone is recommended with amplifiers having fixed gain above
50. Output offset nulling alone is recommended when gain is
fixed at 50 or below.
In applications requiring both initial offsets to be nulled, the
input offset is nulled first by short-circuiting R
offset is nulled with the short removed.
The overall offset voltage drift TCV
a combination of input and output drift specifications. Input
offset voltage drift is multiplied by the amplifier gain, G, and
summed with the output offset drift;
where TCV
the output offset voltage specification. Frequently, the amplifier
drift is referred back to the input (RTI), which is then equiva-
lent to an input signal change;
For example, the maximum input-referred drift of an AMP01 EX
set to G = 1000 becomes;
TCV
INPUT BIAS AND OFFSET CURRENTS
Input transistor bias currents are additional error sources that
can degrade the input signal. Bias currents flowing through the
signal source resistance appear as an additional offset voltage.
Equal source resistance on both inputs of an IA will minimize
offset changes due to bias current variations with signal voltage
and temperature. However, the difference between the two bias
currents, the input offset current, produces a nontrimmable
error. The magnitude of the error is the offset current times the
source resistance.
A current path must always be provided between the differential
inputs and analog ground to ensure correct amplifier operation.
Floating inputs, such as thermocouples, should be grounded
close to the signal source for best common-mode rejection.
REV. D
OS
(RTI ) = 0.3 V/ C +
IOS
V
TCV
OS
and V
IOS
(RTO) = (V
TCV
OS
is the input offset voltage drift, and TCV
(RTO) = (TCV
OOS
OS
IOS
(RTI) = TCV
are the input and output offset voltage
and TCV
IOS
100
G) + V
OOS
IOS
1000
IOS
V C
OS
G) + TCV
/
, referred to the output, is
OOS
TCV
= 0.4 V/ C max
G
OOS
G
OOS
, then the output
OOS
OS
is
(2)
(3)
,
(1)
–11–
GAIN
The AMP01 uses two external resistors for setting voltage gain
over the range 0.1 to 10,000. The magnitudes of the scale resis-
tor, R
G = 20
Figure 29).
The magnitude of R
Circuit performance is characterized using R
operating on 15 volt supplies and driving a 10 volt output. R
may be reduced to 5 k in many applications particularly when
operating on 5 volt supplies or if the output voltage swing is
limited to 5 volts. Bandwidth is improved with R
this also increases common-mode rejection by approximately
6 dB at low gain. Lowering the value below 5 k can cause
instability in some circuit configurations and usually has no
advantage. High voltage gains between two and ten thousand
would require very low values of R
A
limit for R
temperature coefficients will introduce significant gain tempco
errors. Therefore, for gains above 2,000, R
constant at 100
10,000 is obtained with R
Metal-film or wirewound resistors are recommended for best
results. The absolute values and TCs are not too important,
only the ratiometric parameters.
AC amplifiers require good gain stability with temperature and
time, but dc performance is unimportant. Therefore, low cost
metal-film types with TCs of 50 ppm/ C are usually adequate
for R
voltage and gain stability requires precision metal-film or wire-
wound resistors. Achieving a 15 ppm/ C gain tempco at all gains
requires R
5 ppm/ C or better.
V
= 2000 we get R
Figure 29. Basic AMP01 Connections for Gains
0.1 to 10,000
VOLTAGE GAIN, G =
S
S
+IN
–IN
and R
, and gain-set resistor, R
R
G
S
R
S
. Below 100 , mismatch of wirebond and resistor
and R
G
/R
G
. Realizing the full potential of the AMP01’s offset
G
18
2
3
1
, where G is the selected voltage gain (refer to
G
and R
temperature coefficient matching to
G
(
S
AMP01
20
14
R
affects linearity and output referred errors.
= 100 ; this value is the practical lower
S
R
G
S
15
R
S
increased. The maximum gain of
S
)
set to 50 k .
13
10
V+
V–
G
12
11
, are related by the formula:
G
REFERENCE
SENSE
7
8
. For R
9
G
S
S
= 10 k and
should be kept
= 10 k when
OUTPUT
AMP01
S
= 5 k and
S