OPA2277 is a dual-channel version of the high-precision op amp OP277 series introduced by TI's BB company. The single-channel model is OPA277, and the four-channel model is OPA4277. It is an upgraded product of OP07, OP77, OP177 series op amps. Noise, output voltage swing (peak voltage output capability) and double the quiescent current. Other features include very low input offset voltage, low input bias current, high common-mode rejection ratio, and Power supply rejection ratio, channel version consistency (same technical characteristics of series single, dual, and quad op amps).
The OPA277 series op amps have excellent performance in the operating voltage (Vs) range without worrying about adaptability; the offset voltage of this series of op amps has been reduced to the ideal level, usually no need to zero, but the single op amp model is still The zero-setting pins are reserved for specific applications. The multi-channel versions of this family of op amps are identical and independent, providing good crosstalk compliance and reducing mutual interference, even if The same is true for overdrive or overload.
The OPA2277 is available in DIP-8, SO-8 and DFN-8 packages for a variety of installation environments. The outline and pinouts are shown in the figure below. The main technical specifications are shown in the attached table.
The following figure shows the typical characteristic graphs of the OPA2277. For more graphs, please refer to the electronic data files of the OPA277 series op amps. The latest version is SBOS079A.
The voltage range provides negligible performance variations over the ±5V to ±15V supply voltage range, which means the op amp should be easier to use than the ones reported in the report.
From the open-loop input resistance index of the OPA277 series op amps, it is speculated that this series of op amps should belong to the J-FET (junction FET) input type op amp, because its GBW and SR are relatively low, DC and low frequency are high. Accuracy applications should be their strengths, as recommended in their electronic data documents, recommended for sensor (temperature, pressure, etc.) amplifiers, bridge amplifiers, and instrumentation measurement systems. It has been reported that the OPA2277 is applied to audio (such as headphone amplifiers and line amplifiers) and has the "feel" of the tube. I think it might be more accurate to call it the "field effect tube" style. Because this series of op amp noise indicators is better controlled, although the "inflection point" of its distortion characteristic is around 10kHz, because of its extremely low low offset voltage, temperature drift and low noise (relative to J-FET input op amps) Characteristics, for headphone amplification and line amplification should have a good performance, but I believe that for balanced, unbalanced conversion amplifier circuit, DC servo circuit should have better performance, especially the constant current power amplifier circuit highly praised by enthusiasts With high-quality power amplifier circuits, integrated or discrete components, the OPA2277 or OPA277 for DC servo control circuits does not use this expensive high-quality op amp.
The above figure is the two application schematic diagrams of OPA2277 for headphone amplifier. The typical application circuit of line amplification, balance to unbalance, unbalanced balance and DC servo control circuit is more common, so I will not draw it here. I hope it can start. The specific idea is: I hope that the speed and sound field balance characteristics of OPA2277 can be no less than NE5532, and other aspects can be as good as or close to OPA 2 1 34, OPA2227, OPA2604. Figure 4
The above figure (b) is the usage of the OPA2277 as a push. The same adjustment of R22 can adjust the voltage gain of the circuit. The requirements are the same as above. Because the medium-power audio tube is used as the output stage, the ability to push the headphones is greatly enhanced. If the circuit performance is to be improved, the R28 and R29 can be replaced with active electronic filter circuits. However, due to the high PSRR of the OPA2277, the effect may not be obvious. . Adjusting RPl can adjust the working point of the output stage to change the working state of the output stage. Using Class A amplification can of course obtain better sound performance.
The above picture is another kind of amp circuit, which is derived from the power amplifier circuit. The shadow of this circuit can also be seen in some famous machines. This kind of circuit is called the reverse-emitter follower complementary circuit. There are many forms of circuit change. The characteristic of Figure 5 is that there is no big loop feedback, the sound is thick and the bass is powerful, just enough to match the earphone to get the best sound performance. A slight distortion can also be used to drive a high-quality amplifier for the speaker. This kind of circuit is currently provided by many domestic audio mail purchasers, including the empty board, the price is not expensive, so it is recommended for the fans who want to use the standard printed board to test. The op amp in Figure 5 can have a variety of options, such as NE5532, OPA2134, etc., the power supply voltage can be ± 18V.
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