5
Application Information
Power Supply Decoupling
Although not absolutely necessary, it is recommended that
all power supply lines be decoupled with 0.01
μ
F ceramic
capacitors to ground. Decoupling capacitors should be
located as near to the amplifier terminals as possible.
Considerations For Prototyping:
The following list of recommendations are suggested for
prototyping.
1. Resolving low level signals requires minimizing leakage
currents caused by external circuitry. Use of quality
insulating materials, thorough cleaning of insulating
surfaces and implementation of moisture barriers when
required is suggested.
2. Error voltages generated by thermocouples formed
betweendissimilarmetalsinthepresenceoftemperature
gradients should be minimized. Isolation of low level
circuity from heat generating components is
recommended.
3. Shielded cableinputleads,guardrings andshielddrivers
are recommended for the most critical applications.
Large Capacitive Loads
When driving large capacitive loads (>500pF), a small value
resistor (
≈
50
) should be connected in series with the
output and inside the feedback loop.
Offset Voltage Adjustment (See Figure 3)
A 20k
balance potentiometer is recommended if offset
nulling is required. However, other potentiometer values
such as 10k
, 50k
and 100k
may be used. The
minimum adjustment range for given values is
±
2mV. V
OS
TC of the amplifier is optimized at minimal V
OS
. Tested
Offset Adjustment is |V
OS
+ 1mV| minimum referred
to output.
Saturation Recovery
Input and output saturation recovery time is negligible in
most applications. However, care should be exercised to
avoid exceeding the absolute maximum ratings of the
device.
Differential Input Voltages
Inputs are shunted with back-to-back diodes for overvoltage
protection. In applications where differential input voltages in
excess of 1V are applied between the inputs, the use of
limiting resistors at the inputs is recommended.
Typical Applications
The excellent input and gain characteristics of HA-5135 are
well suited for precision integrator applications. Accurate
integration over seven decades of frequency using HA-5135,
virtually nullifies the need for more expensive chopper-type
amplifiers.
Low V
OS
coupled with high open loop Gain, high CMRR
and high PSRR make HA-5135 ideally suited for precision
detector applications, such as the zero crossing detector
shown in Figure 5.
2
6
1
7
8
V+
+
4
3
5
R
P
(NOTE)
20k
OPTIONAL
CONNECTION
-
FIGURE 3. OFFSET NULLING CONNECTIONS
2
1
7
8
+
4
3
5
R
B
C
6
R
OUT
-
FIGURE 4. PRECISION INTEGRATOR
HA-5135