SBOS110B May   1998  – June 2015 OPA2227 , OPA2228 , OPA227 , OPA228 , OPA4227 , OPA4228

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information: OPA227U/UA and OPA228U/UA
    5. 6.5 Thermal Information: OPA227P/PA and OPA228P/PA
    6. 6.6 Electrical Characteristics: OPAx227 Series (VS = ±5 V to ±15 V)
    7. 6.7 Electrical Characteristics: OPAx228 Series (VS = ±5 V to ±15 V)
    8. 6.8 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Offset Voltage and Drift
      2. 7.3.2 Operating Voltage
      3. 7.3.3 Offset Voltage Adjustment
      4. 7.3.4 Input Protection
      5. 7.3.5 Input Bias Current Cancellation
      6. 7.3.6 Noise Performance
      7. 7.3.7 Basic Noise Calculations
      8. 7.3.8 EMI Rejection Ratio (EMIRR)
        1. 7.3.8.1 EMIRR IN+ Test Configuration
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Three-Pole, 20 kHz Low Pass, 0.5-dB Chebyshev Filter
      2. 8.1.2 Long-Wavelength Infrared Detector Amplifier
      3. 8.1.3 High Performance Synchronous Demodulator
      4. 8.1.4 Headphone Amplifier
      5. 8.1.5 Three-Band Active Tone Control (Bass, Midrange, and Treble)
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Using the OPAx228 in Low Gains
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 TINA-TI (Free Software Download)
        2. 11.1.1.2 TI Precision Designs
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The OPAx22x series are precision operational amplifiers with very low noise. The OPAx227 series is unity-gain stable with a slew rate of 2.3 V/μs and 8 MHz bandwidth. The OPAx228 series is optimized for higher-speed applications with gains of 5 or greater, featuring a slew rate of 10 V/μs and 33-MHz bandwidth. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins. In most cases, 0.1-μF capacitors are adequate.

8.1.1 Three-Pole, 20 kHz Low Pass, 0.5-dB Chebyshev Filter

OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_14_three_pole_20khz_sbos110.gifFigure 45. Three-Pole, 20 kHz Low Pass, 0.5-dB Chebyshev Filter

8.1.2 Long-Wavelength Infrared Detector Amplifier

OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_15_long_wvlngth_infrd_dtctr_amp_sbos110.gifFigure 46. Long-Wavelength Infrared Detector Amplifier

8.1.3 High Performance Synchronous Demodulator

OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_16_high_perf_sync_demod_sbos110.gifFigure 47. High Performance Synchronous Demodulator

8.1.4 Headphone Amplifier

OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_17_headphone_amp_sbos110.gifFigure 48. Headphone Amplifier

8.1.5 Three-Band Active Tone Control (Bass, Midrange, and Treble)

OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_18_3_band_act_tone_ctrl_sbos110.gifFigure 49. Three-Band Active Tone Control (Bass, Midrange, and Treble)

8.2 Typical Application

OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 OPAx227_Typ_App_Ckt_SBOS110.gifFigure 50. Typical Application Schematic

8.2.1 Design Requirements

  1. Operate OPAx228 gain is less than 5 V/V
  2. Stable operation with capacitive load

8.2.2 Detailed Design Procedure

8.2.2.1 Using the OPAx228 in Low Gains

The OPAx228 family is intended for applications with signal gains of 5 or greater, but it is possible to take advantage of their high-speed in lower gains. Without external compensation, the OPA228 has sufficient phase margin to maintain stability in unity gain with purely resistive loads. However, the addition of load capacitance can reduce the phase margin and destabilize the operational amplifier.

A variety of compensation techniques have been evaluated specifically for use with the OPA228. The recommended configuration consists of an additional capacitor (CF) in parallel with the feedback resistance, as shown in Figure 51 and Figure 52. This feedback capacitor serves two purposes in compensating the circuit. The operational amplifier’s input capacitance and the feedback resistors interact to cause phase shift that can result in instability. CF compensates the input capacitance, minimizing peaking. Additionally, at high frequencies, the closed-loop gain of the amplifier is strongly influenced by the ratio of the input capacitance and the feedback capacitor. Thus, CF can be selected to yield good stability while maintaining high-speed.

Without external compensation, the noise specification of the OPA228 is the same as that for the OPA227 in gains of 5 or greater. With the additional external compensation, the output noise of the of the OPA228 will be higher. The amount of noise increase is directly related to the increase in high-frequency closed-loop gain established by the CIN/CF ratio.

Figure 51 and Figure 52 show the recommended circuit for gains of 2 and –2, respectively. The figures suggest approximate values for CF. Because compensation is highly dependent on circuit design, board layout, and load conditions, CF should be optimized experimentally for best results. Figure 53 and Figure 55 show the large- and small-signal step responses for the G = 2 configuration with 100-pF load capacitance.Figure 54 and Figure 56 show the large- and small-signal step responses for the G = –2 configuration with 100-pF load capacitance.

OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_08_compmstn_opa228_sbos110.gifFigure 51. Compensation of the OPA228 for G = 2
OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_11_compstn_opa228_sbos110.gifFigure 52. Compensation for OPA228 for G = –2

8.2.3 Application Curves

OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_09_lssr_sbos110.gifFigure 53. Large-Signal Step Response, G = 2,
CLOAD = 100 pF, Input Signal = 5 Vp-p
OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_10_sssr_sbos110.gifFigure 55. Small-Signal Step Response, G = 2,
CLOAD = 100 pF, Input Signal = 50 mVp-p.
OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_12_lssr_sbos110.gifFigure 54. Large-Signal Step Response, G = –2, CLOAD = 100 pF, Input Signal = 5 Vp-p
OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228 app_info_13_sssr_sbos110.gifFigure 56. Small-Signal Step Response, G = –2,
CLOAD = 100 pF, Input Signal = 50 mVp-p.