Features

● Low distortion: 0.0003%at 1kHz

● Low noise: 10nv/√Hz

● High conversion rate: 25V/μs

● Width increase bandwidth: 20MHz

● The unit gain stable

● The range of power supply is wide: vs u003d ± 4.5 to ± 24v

● Drive 600 load

● Provide dual versions (OPA2604)

Application

● Professional audio equipment

● PCM DAC I/V converter

● spectral analysis equipment

● Active filter

● Sensor amplifier

● Data collection

OPA604 is a fET Enter the computing amplifier to enhance communication performance. Very low distortion, low noise and broadband bands provide excellent performance in high -quality audio and other applications that need excellent dynamic performance.

New circuit technology and special laser fine -tuning dynamic circuit performance produce very low harmonic distortion. As a result, an excellent computing amplifier with excellent sound quality. The low noise FET input of OPA604 provides a wide dynamic range and even high source impedance. The bias voltage is a laser fine -tuning to reduce the needs of the interstitial coupling capacitor.

The surface temperature range is -25 ° C to -8 ° C, which is suitable for the minimum temperature range of OPA-8.

pin configuration

Typical features

TA u003d+25 ° C, vs u003d ± 15V, unless there is another explanation.

Application information offset voltage adjustment [

123] OPA604 bias voltage is laser fine -tuning, and no further fine -tuning is needed in most applications. Like most amplifiers, for adjustments per 100 μV, external fine -tuning remaining offset can change the drift performance about 0.3 μV/° C. OPA604 can replace many other amplifiers by non -connected external zero circuits.

OPA604 is a stable unit gain, making it easy to use in a wide range of circuits. For the application of noise or high impedance power cord, it is necessary to use an anti -coupling capacitor near the device pins. In most cases, it is enough to install 1 μF 钽 capacitors on each power pins.

distortion measurement

The distortion generated by OPA604 is lower than the measurement limit of almost all commercial equipment. However, a special test circuit can be used to expand the measurement capabilities.

The incompetence of the computing amplifier can be regarded as an internal error source, and you can refer to the input. Figure 2 shows a circuit that causes 101 times the distortion of the operation amplifier distortion than the normal production amplifier. Adding R3 to other standards of non -mute amplifier configuration will change the feedback coefficient or noise gain of the circuit. The closed -loop gain is unchanged, but the feedback that can be used for error correction is reduced by 101 times. This will expand the measurement limit (including the impact of signal source purity) by 101 times. Note that the input signal and load of the application to the computing amplifier are the same as the traditional feedback without R3.

The effectiveness of this technology can be verified by repeated measurement under high gain and/or high frequency, where the distortion is within the measurement capacity range of the test equipment. The measurement of this data table is performed with audio precision system 1, which greatly simplifies repeated measurement. However, the measurement technology can be executed by manual distortion measuring instruments.

Capacity load

The dynamic characteristics of OPA604 have been optimized for common gain, load and working conditions. The combination of low -closed cycle gain and capacitance load will reduce phase margin, and may lead to peak or oscillation of gain. The load capacitance and the opening output resistance reaction of the computing amplifier form an extra pole in the feedback loop. Figure 3 shows a variety of circuits that maintain phase margin under the capacitance load.

For the unit gain buffer, as shown in Figure 3A, it maintains stability by adding phase advance network RC and CC. The voltage of crossing RC will reduce the output voltage swing when the heavy load is loaded. The spare circuit shown in Figure 3B does not limit the output of low load impedance. It provides a small amount of positive feedback to reduce the net feedback coefficient. Due to the decrease in the attenuation of the operation amplifier, the self -lifting effect on the compensation network, the input impedance of the circuit decreased down at high frequency.

FIG. 3C and 3D displayed compensation techniques for non -conversion amplifiers. Like the follower circuit, the circuit in Figure 3D eliminates the voltage drop caused by the load current, but the cost is reduced by the high -frequency input impedance.

FIG. 3E and 3F show the input lead compensation network for inverter and differential amplifier configuration.

Noise performance

The noise of the operation amplifier is described by two parameters: noise voltage and noise current. Voltage noise determines the noise performance under low source impedance. Low noise bipolar input computing amplifiers, such as OPA27 and OPA37 offers very low voltage noise. However, if the source impedance is greater than thousands of ohms, the current noise of the bipolar input computing amplifier will respond to the source impedance and dominate the position. Under thousands of ohms and above sources, OPA604 usually offers lower noise.

Power loss

OPA604 can drive 600 load, and the power supply voltage is as high as ± 24V. When working at a high power supply voltage, the internal power consumption increases. Typical characteristic curves, power loss and power voltage, display static dissipation (no signal or no load) and the worst case of continuous sine wave dispersing. Continuous high -level music signals are usually scattered much smaller than the worst cases.

Compared with traditional plastic packaging, the copper quotation frame structure used in OPA604 improves heat dissipation. In order to achieve the best heat dissipation effect, the equipment is directly welded to the circuit board and marks with a width circuit board.

The output current limit

The output current is limited by the internal circuit to about ± 40 mAh at 25 ° C. As shown in the typical curve, the extreme current decreases with the temperature increase.

Note: The design formula and component value are approximate values. Users need to adjust to get the best performance.

Sound quality The discussion of the surface is provided, and it is not all of the performance that is measured. Actions can be explained or related to the hearing test of audio experts. The design of OPA604 takes into account the objective performance measurement, but also the awareness of the extensive theory of the successful and failure of the previous op amp. sound quality

The sound quality of the operation amplifier is usually the key selection criteria, even if the data table claims that it has abnormal distortion performance. In terms of nature, sound quality is subjective. In addition, the results of hearing tests may vary from application and circuit configuration. Even experienced listeners often come to different conclusions in the control test.

Many audio experts believe that the sound quality of high -performance FET computing amplifiers is better than bipolar computing amplifiers. One possible reason is that the double pole design produces a larger strange harmonic than FET. For human ears, the number of strange horses has always been considered to be more unhappy than the harmonic waves. FET, like a vacuum tube, has the I-V transmission function of a square law, which is more linear than the exponential transmission function of the bipolar transistor. As a direct result of the characteristics of the square law, FET mainly produces occasional harmonics several times. Figure 10 shows the transmission function of the bipolar transistor and field effect transistor. The Fourier transformation of the two transmitting functions reveals the low -second harmonic hormone of the field effect transistor amplifier level.

OPA604 Design

OPA604 uses FET throughout the signal channel, including the important phase of the input level, input level load and output level important part of the part. Essence Billar crystals are important for their characteristics (such as current capacity), and their transmissionPower that has the least influence.

The topology consists of a folding co -source grid increase level and unit gain output level.Differential input transistor J1 and J2 are a special large -sized P channel JFET.The input level current is a relatively high 800 μA, which provides high -crossing and low -voltage noise.Class current laser fine -tuning and careful attention to the symmetry generated a near -symmetrical conversion rate of ± 25V/μs. The input level of the JFET will keep the input bias current at about 50Pa or about 3,000 times lower than that of an audio amplifier.This greatly reduces the noise of high impedance circuits.

The drain of J1 and J2 is counted by Q1 and Q2, and the input level load load FETJ3 and J4.Line -based opening response and increased voltage gain in distortion inhibitory circuit (patent).The 20MHz bandwidth of OPA604 further reduces distortion through the feedback circuit of user connection.

The output level includes a JFET partner loaded to a high -speed full NPN output drive.The output transistor is biased by a special circuit to prevent cutting, even if the output width reaches 600