OPA1678 Datasheet, PDF (18/41 Pages) Texas Instruments – Low-Distortion Audio Operational Amplifiers

OPA1678, OPA1679
SBOS855 – FEBRUARY 2017
www.ti.com
7.3.3.1 EMIRR IN+ Test Configuration
Figure 34 shows the circuit configuration for testing the EMIRR IN+. An RF source is connected to the
operational amplifier noninverting input pin using a transmission line. The operational amplifier is configured in a
unity-gain buffer topology with the output connected to a low-pass filter (LPF) and a digital multimeter (DMM). A
large impedance mismatch at the operational amplifier input causes a voltage reflection; however, this effect is
characterized and accounted for when determining the EMIRR IN+. The resulting dc offset voltage is sampled
and measured by the multimeter. The LPF isolates the multimeter from residual RF signals that can interfere with
multimeter accuracy. See the EMI Rejection Ratio of Operational Amplifiers application report for more details.
Ambient temperature: 25Û&
RF source
DC Bias: 0 V
Modulation: None (CW)
Frequency Sweep: 201 pt. Log
+VS
±
50
+
-VS
Not shown: 0.1 µF and 10 µF
supply decoupling
Low-Pass Filter
Sample /
Averaging
Digital Multimeter
Figure 34. EMIRR IN+ Test Configuration Schematic
7.4 Device Functional Modes
7.4.1 Operating Voltage
The OPA167x series op amps operate from ±2.25 V to ±18 V supplies while maintaining excellent performance.
The OPA167x series can operate with as little as 4.5 V between the supplies and with up to 36 V between the
supplies. However, some applications do not require equal positive and negative output voltage swing. With the
OPA167x series, power-supply voltages are not required to be equal. For example, the positive supply can be
set to 25 V with the negative supply at –5 V.
In all cases, the common-mode voltage must be maintained within the specified range. In addition, key
parameters are ensured over the specified temperature range of T_A = –40°C to +85°C. Parameters that vary
significantly with operating voltage or temperature are shown in the Typical Characteristics section.
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