SBOA510 March   2021 OPA455 , OPA462

 

  1.   Trademarks
  2. 1Introduction
  3. 2Three Op Amp OPA462 HV Solution
  4. 3Lower Voltage, Lower Cost Three Op Amp Solution
  5. 4OPA462 300 Vpp Output Solution With Discrete Transistor Supply-Rail Drivers
  6. 5Lessons Learned from the Practical Implementation of the HV Op Amp Solutions
  7.   A Appendix
    1.     A.1 Overview
    2.     A.2 Summary of Results
    3.     A.3 Test Setup and Equipment
    4.     A.4 Printed Circuit Boards
    5.     A.5 Power Supply, Source Measurement Unit (SMU)
    6.     A.6 Arbitrary Waveform Generator (AWG)
    7.     A.7 Oscilloscope
    8.     A.8 Circuit 1: OPA462 Three op amp Solution
      1.      A.8.1 Schematic
      2.      A.8.2 Conventions
      3.      A.8.3 Results
    9.     A.9 Circuit 2: Lower Voltage, Lower Cost Three Op Amp Solution
      1.      A.9.1 Schematic
      2.      A.9.2 Conventions
      3.      A.9.3 Results
    10.     A.10 Circuit 3: OPA462 300 Vpp Output Solution With Discrete Transistor Supply-Rail Drivers
      1.      A.10.1 Schematic
      2.      A.10.2 Conventions
      3.      A.10.3 Results

5 Lessons Learned from the Practical Implementation of the HV Op Amp Solutions

The OPA462 HV circuits presented have been built and tested in our TI Precision Amplifiers Applications lab. Section A provides the measured results for each circuit The circuits in the general description section and those shown in Section A have some minor differences that can include different closed-loop gain settings, some component value differences and numbering, and added HV protection to assure reliable long-term operation. HV circuits may be subjected to transient conditions that could damage the op amps if external protection is not included in the circuits.

Additionally, the OPA462 HV op amp has an enable/shutdown function that can be selected to place the op amp in normal op amp mode, or to shut down the output stage when operation is not required. In the latter case, the operating current is highly reduced. The enable/shutdown pin needs to be properly biased to assure one state of operation or the other. The OPA462 High-Voltage (180-V), High-Current (30-mA) Operational Amplifier Data Sheet provides complete information how to apply and configure the enable/shutdown function.

When the OPA462 is applied alone, and not one of the HV boot-strap circuits, the enable/shutdown pin can be left floating. It has a “weak” internal current source that pulls the pin high, enabling the output stage. However, when the OPA462 is used in an HV boot-strap circuit where the supply pins move along with the output, it is recommended that the op amp be set in enable mode. A strong external bias source such as a resistive voltage divider, or low impedance voltage source, is ideal. It was observed in bench tests that circuit noise coupled to the high impedance enable pin could actually unintentionally and momentarily shut down the OPA462 output during a noisy period.