Features

● Low noise: maximum 4.5NV/√Hz when 1kHz

● Data collection

● Test equipment

] ● Professional audio equipment

● Sensor amplifier

● radiation protection equipment

OPA27

OPA37 [ 123] It is an ultra -low -noise, high -precision single -chip calculation amplifier. Compared with ordinary Zina-Zapp technology, laser trimming thin film resistors provide excellent long-term voltage offset stability and allow superior voltage offsets. The unique bias current elimination circuit allows the bias and bias current specifications throughout -40 ° C to+85 ° C.

OPA27 internal compensation for unified gain stability. OPA37 requires a closed -loop gain ≥5.

OPA27 and OPA37 of Texas Instruments are industry standards OP-27 and OP-37 improved alternatives.

TA +25 ° C, ± VCC ± 15VDC, unless there is another instructions.

Application information [123 ] Adjustment of offset voltage OPA27 and OPA37 bias voltage after laser repair, most applications do not need to be further trimmed. When using 10K fine -tuning potential meter to make the input offset zero, the offset voltage drift will not decrease. You can use other potential values of 1K to other potentials of 1M but VOS drift will reduce 0.1 μV/° C to 0.2 μV/° C. The system offset that uses offset fine -tuning adjustments will reduce the drift performance by about 3.3 μV/° C per millivolt. By input, you can make the large system shift to zero without reducing the drift. The traditional bias voltage fine -tuning circuit is shown in Figure 3. For the very small offset of fine -tuning, it is recommended to use in Figure 4 moreHigh -resolution circuit.

OPA27 and OPA37 can replace the 741 computing amplifier by removing or modifying a fine -tuning circuit.

Thermal potential

OPA27 and OPA37 are laser fine -tuning to micro -level input offset voltage, and used for very low input offset voltage drift.

Careful layout and circuit design technology is a necessary condition for preventing external thermal power from generating offset and drift errors. If they accidentally eliminate their sources (PC, Wiring, etc.) or their temperature differences (see Figure 11), alien metal knots may produce small EMFs.

It is highly recommended to install OPA27 and OPA37 short distances, and the spinning spacing is small. Poor layout can lead to circuit drift and offset, and its order is one magnitude larger than a separate computing amplifier.

Noise: Bilateral and field -effect transistor

The design of low noise circuit needs to carefully analyze all noise sources. In many cases, external noise sources dominate, so the effect of source resistance on the overall noise performance of the operation amplifier must be considered. Under the low -source impedance, the low -voltage noise of the bipolar operational amplifier is better than the bi -pole calculation amplifier, but under high impedance, the high -current noise of the bipolar amplifier has become a serious problem. At 15K above, it is recommended to use OPA111 low noise FET computing amplifier to obtain a lower total noise than OPA27, as shown in Figure 5.

Compensation

Although the internal compensation of the unit gain stability, OPA27 may require a small capacitor and a 2K #8486 The feedback resistance (RF) parallel. The capacitor will compensate the electrodes generated by radio frequency and CIN to eliminate peak or oscillation.

Input protection Back -to -back diode for input protection for OPA27 and OPA37. The input signal of more than a few hundred millivolves will cause current flow. If there is no external current limiting resistor, the input will be destroyed.