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参数资料
| 型号： | 176K |
| 元件分类： | 运算放大器 |
| 英文描述： | OP-AMP |
| 文件页数： | 3/5页 |
| 文件大小： | 238K |
| 代理商： | 176K |
A
3
http://www.calex.com
2401 Stanwell Drive
Concord, CA 94520-4841
(510) 687-4411 Fax (510) 687-3333
CALEX
FaxFACTS:
320
1997
Operation and Adjustment
Figure 10 shows pin connections for the Model 176 when
used with external offset trim. Offset is quite low on the
untrimmed unit and external trimming is normally not needed.
If external trimming is used and ambient temperature varies
widely, a potentiometer and resistor with good temperature
coefficient should be used. Range of adjustment is ±3 mV
referred to the input. Gain is adjusted by means of Rg which
should be a low power, temperature stable, precision resistor.
The wire leads to Rg should be kept as short as possible to
avoid noise pickup. If it is necessary to locate Rg some
distance from the amplifier, a shielded twisted pair should be
used for the connection.
There must be a current path from the amplifier inputs to
power supply common to allow the input bias current to flow.
A floating signal source can generally be accommodated by
connecting a 1 M
resistor between input signal ground and
the amplifier common. This provides a return path for the
amplifier input bias current.
FIGURE 8.
Common Mode Rejection (CMR)
The Model 176 provides excellent CMR at DC and higher
frequencies. One of the frequencies of interest is 60 Hz and
it can be seen from Figure 8 that the CMR is virtually
unchanged from DC to 60 Hz. Higher frequencies are important
also and the Model 176 maintains good CMR to over 1 kHz.
For example, it may be desired to operate a bridge circuit with
an AC voltage source such as 400 Hz. The Model 176 can still
function as a differential bridge amplifier with a CMR of almost
100 dB (G = 100) at that frequency.
FIGURE 7.
100
1000
10000
100000
1000000
FREQUENCY - Hz
0
20
40
60
80
100
GAIN
-
db
TYPICAL SMALL SIGNAL FREQUENCY RESPONSE
G = 10
G = 100
G = 1000
5000
.1
1
10
100
1000
FREQUENCY (Hz)
60
70
80
90
100
110
120
130
140
COMMON
MODE
REJECTION
-
db
CMR Vs. FREQUENCY
G = 1000
G = 100
G = 10
Theory of Operation
In Figure 6, the amplifier differential gain is:
Vout = 1 + Rf +2 Rf
V1 - V2
RE
Rg
Rf
is chosen to be precisely 9 ±0.05%
RE
Since Rf is equal to 100 k
, this results in a gain equation of
Vout
= 10 + 200 k
V1 - V2
Rg
The accuracy of this equation depends on careful matching
of the various resistors and the quality of the transistor input
pair. The Model 176 uses a special input pair that is designed
especially for high performance instrument amplifiers. Diodes
between base and emitter provide input protection of up to
±20 Volts differential or common mode.
To provide the ultimate in CMR, a separate operational
amplifier is used to feedback common-mode voltage to the
input pair. A Common-mode voltage is generated across Rcm
which is then fed into the common-mode amplifier input. This
amplifier also serves as a current source for the input
differential pair. Since some gain is provided by the input
transistor, the op amp is operated at lower closed loop gains
allowing gain linearity and bandwidth to be significantly better
than when all gain is provided by a single op amp.
FIGURE 6. Simplified Schematic of Model 176
Frequency Response
Bode plots of the Model 176 gain for gains of 10,100 and 1000
are shown in Figure 7. The frequency response has been
designed to equal a single pole roll-off with a damping ratio of
approximately 0.7. This prevents a ringing response if the
amplifier is used with square wave or pulse input signals. Gain
error is less than ±1% and phase shift is less than 6° at
frequencies lower than 1 /10 of the 3 dB down frequency for
any gain. If gain accuracy of better than ±0.1 % is desired,
gain magnitude should be adjusted so that the highest signal
frequency to be amplified is less than 0.05 times the 3 dB
down frequency.
Model 176 DC Differential Amplifier
相关PDF资料 |
PDF描述 |
|---|---|
| 176L | OP-AMP |
| 178 | OP-AMP |
| 1782-97H | 1 ELEMENT, 0.13 uH, PHENOLIC-CORE, GENERAL PURPOSE INDUCTOR |
| 1782-97F | 1 ELEMENT, 0.13 uH, PHENOLIC-CORE, GENERAL PURPOSE INDUCTOR |
| 1782-95F | 1 ELEMENT, 0.11 uH, PHENOLIC-CORE, GENERAL PURPOSE INDUCTOR |
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