OPA1632 Datasheet, PDF (12/30 Pages) Texas Instruments – High-Perfomance, Fully-Differential AUDIO OP AMP

OPA1632
SBOS286C – DECEMBER 2003 – REVISED OCTOBER 2015
8 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
8.1.1 Output Common-Mode Voltage
The output common-mode voltage pin sets the dc output voltage of the OPA1632. A voltage applied to the V_OCM
pin from a low-impedance source can be used to directly set the output common-mode voltage. For a V_OCM
voltage at mid-supply, make no connection to the V_OCM pin.
Depending on the intended application, a decoupling capacitor is recommended on the V_OCM node to filter any
high-frequency noise that could couple into the signal path through the V_OCM circuitry. A 0.1-μF or 1-μF capacitor
is generally adequate.
Output common-mode voltage causes additional current to flow in the feedback resistor network. Since this
current is supplied by the output stage of the amplifier, this creates additional power dissipation. For commonly-
used feedback resistance values, this current is easily supplied by the amplifier. The additional internal power
dissipation created by this current may be significant in some applications and may dictate use of the MSOP
PowerPAD package to effectively control self-heating.
8.1.1.1 Resistor Matching
Resistor matching is important in fully-differential amplifiers. The balance of the output on the reference voltage
depends on matched ratios of the resistor. CMRR, PSRR, and cancellation of the second-harmonic distortion
diminish if resistor mismatch occurs. Therefore, it is recommended to use 1% tolerance resistors or better to
keep the performance optimized.
V_OCM sets the dc level of the output signals. If no voltage is applied to the V_OCM pin, it is set to the midrail voltage
internally defined as:
(V_CC+ )+ (V_CC- )
2
(1)
In the differential mode, the V_OCM on the two outputs cancel each other. Therefore, the output in the differential
mode is the same as the input in the gain of 1. V_OCM has a high bandwidth capability up to the typical operation
range of the amplifier. For the prevention of noise going through the device, use a 0.1-µF capacitor on the V_OCM
pin as a bypass capacitor. The Functional Block Diagram shows the simplified diagram of the OPA1632.
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