SBOU268 November   2021 OPA593

 

  1.   Trademarks
  2. 1Overview
    1. 1.1 Getting Started
      1. 1.1.1 Related Documentation From Texas Instruments
    2. 1.2 High-Voltage Warning and Safe Use
    3. 1.3 Electrostatic Discharge Caution
  3. 2Operation
    1. 2.1 Jumper Blocks, Jacks, and Test Points
    2. 2.2 Inputs
    3. 2.3 Outputs
    4. 2.4 Enable or Disable
    5. 2.5 Status Flags
      1. 2.5.1 Circuit Protection
  4. 3Application Circuits
    1. 3.1 Setting Dual-Supply or Single-Supply Operation
      1. 3.1.1 Dual-Supply Operation Configuration
      2. 3.1.2 Single-Supply Operation Configuration
    2. 3.2 Common Op-Amp Configurations
      1. 3.2.1 Inverting Gain of –10 V/V
        1. 3.2.1.1 External Connections for –10 V/V Inverting Gain Configuration
        2. 3.2.1.2 Inverting Gain of –10 V/V Configuration Electrical Performance
      2. 3.2.2 Noninverting Gain of +2 V/V
        1. 3.2.2.1 External Connections to OPA593EVM for Noninverting Gain Configuration
        2. 3.2.2.2 Noninverting Gain Configuration Electrical Performance
      3. 3.2.3 Gain of +10 V/V Difference Amplifier
        1. 3.2.3.1 Jumper Shunt Locations for Difference-Amplifier Configuration
        2. 3.2.3.2 Gain of 10 V/V Difference Amplifier Configuration Electrical Performance
      4. 3.2.4 Improved Howland Current Pump
        1. 3.2.4.1 Jumper Shunt Locations for Improved Howland Current Pump Configuration
  5. 4Schematic, PCB Layout, and Bill of Materials
    1. 4.1 EVM Schematic
      1. 4.1.1 EVM Default Configuration
    2. 4.2 PCB Layout
    3. 4.3 Bill of Materials

3.2.4.1 Jumper Shunt Locations for Improved Howland Current Pump Configuration

Connect the intended voltages or signal sources to the OPA593EVM VIN+ and VIN– jacks using a 50-Ω coaxial cable with standard male BNC connectors for each jack. In most cases, the easiest connection method for the Improved Howland current pump is to connect the output load to the J12 VOUT terminal block and the respective GND. To monitor the current (±) being provided by the OPA593 output, connect an ammeter in series with the load. Connect and apply the required supply voltages to the V+, V–, and GND jacks. Turn on the input voltage or signal source (or sources) and verify the circuit functions as expected.

The IOUT current is a function of the difference in voltages or signals applied to VIN+ J9 and VIN– J5. For the specific condition set up on the OPA593EVM where Ri1 = RF1 = R4 = Rhcp1 = 10 kΩ, the transfer function is simply:

Equation 4. I O U T = V I N+ – V I N– R i s o 2

Riso2 = 49.9 Ω is a constant that scales the IOUT output current. The scaling is different when Riso is set to a different value. Select the value of Riso2 so that the current range coincides with the OPA593 data sheet specifications.

Practically, the OPA593 improved Howland current pump circuit can provide the IOUT current through a very-low load resistance of a few Ohms. The high-end voltage is limited by the op amp output voltage compliance range, which is in proportion to the supply voltages being used.