OPA1641-Q1 Datasheet, PDF (13/31 Pages) Texas Instruments – SoundPlus JFET-Input, Automotive-Grade, Audio Operational Amplifiers

www.ti.com
OPA1641-Q1, OPA1642-Q1
SBOS791 – JUNE 2017
7.3 Feature Description
7.3.1 Phase Reversal Protection
The OPA164x-Q1 family has internal phase-reversal protection. Many op amps exhibit phase reversal when the
input is driven beyond the linear common-mode range. This condition is most often encountered in noninverting
circuits when the input is driven beyond the specified common-mode voltage range, causing the output to
reverse into the opposite rail. The input of the OPA164x-Q1 prevents phase reversal with excessive common-
mode voltage. Instead, the appropriate rail limits the output voltage. This performance is shown in Figure 29.
Output
+18 V
OPA1641-Q1
-18 V
37 VPP
Sine Wave
(±18.5 V)
Output
Time (0.4 ms/div)
Figure 29. Output Waveform Devoid of Phase Reversal During an Input Overdrive Condition
7.3.2 Output Current Limit
The output current of the OPA164x-Q1 series is limited by internal circuitry to 36 mA and –30 mA (sourcing and
sinking), to protect the device if the output is accidentally shorted. This short-circuit current depends on
temperature; see Figure 26.
Although uncommon for most modern audio applications to require 600-Ω load drive capability, many audio
operational amplifier applications continue to specify the total harmonic distortion (THD+N) at 600-Ω load for
comparative purposes. Figure 7 and Figure 8 provide typical THD+N measurement curves for the OPA164x-Q1
series, where the output drives a 3-V_RMS signal into a 600-Ω load. However, correct device operation cannot be
ensured when driving 600-Ω loads at full supply. Depending on supply voltage and temperature, this operating
condition can possibly trigger the output current limit circuitry of the device.
7.3.3 EMI Rejection Ratio (EMIRR)
The electromagnetic interference (EMI) rejection ratio, or EMIRR, describes the EMI immunity of operational
amplifiers. An adverse effect that is common to many operational amplifiers is a change in the offset voltage as a
result of RF signal rectification. An operational amplifier that is more efficient at rejecting this change in offset as
a result of EMI has a higher EMIRR and is quantified by a decibel value. Measuring EMIRR can be performed in
many ways, but this document provides the EMIRR IN+, which specifically describes the EMIRR performance
when the RF signal is applied to the noninverting input pin of the operational amplifier. In general, only the
noninverting input is tested for EMIRR for the following three reasons:
• Operational amplifier input pins are known to be the most sensitive to EMI, and typically rectify RF signals
better than the supply or output pins.
• The noninverting and inverting operational amplifier inputs have symmetrical physical layouts and exhibit
nearly matching EMIRR performance.
• EMIRR is easier to measure on noninverting pins than on other pins because the noninverting input pin can
be isolated on a printed-circuit-board (PCB). This isolation allows the RF signal to be applied directly to the
noninverting input pin with no complex interactions from other components or connecting PCB traces.
A more formal discussion of the EMIRR IN+ definition and test method is provided in application report EMI
Rejection Ratio of Operational Amplifiers, available for download at www.ti.com.
Copyright © 2017, Texas Instruments Incorporated
Submit Documentation Feedback
13
Product Folder Links: OPA1641-Q1 OPA1642-Q1