Voltage to Current Converter Using Op-Amp

Introduction

• Topic: Design of voltage to current converter using operational amplifier (op-amp)
• Importance in industrial applications and instrumentation

Need for Voltage to Current Conversion

• Industrial Applications:

  • Sensors (e.g., temperature) output voltage
  • Issues:
    • Voltage drop during transportation
    • Noise superimposition
  • Solution: Convert voltage to current
    • Current remains constant over distance
    • Less prone to noise

• Laboratory Applications:

  • Useful for testing circuit components
  • Driving LEDs

Passive Voltage to Current Converter

• Basic design:
  • Connect resistor in series with voltage source
• Relation:
  • Load current (I) depends on load resistor (R)
  • Ideal current should depend only on input voltage

Active Voltage to Current Converter

• Known as Floating Load Converter

• Circuit Design:

  • Input applied at non-inverting terminal
  • Negative feedback creates virtual short between terminals
  • Current through resistor (R) equals load current (IL)
  • Load current (IL) proportional to input voltage (Vin)

• Applications:

  • Driving LEDs: Constant current for varying input voltage
  • Matching pairs of diodes/Zener diodes:
    • Measure output voltage to find matched components

Grounded Load Voltage to Current Converter

• Load is grounded

• Circuit Analysis:

  • Define node (A), voltage (V1), and load current (IL)
  • Apply Kirchhoff's Current Law (KCL):
    • I1 + I2 = IL
  • Expressions for I1 and I2:
    • I1 = (Vin - V1) / R
    • I2 = (Vout - V1) / R

• Output Voltage Relation:

  • Vout = (1 + Rf/R) * V1 where Rf = feedback resistor, R = input resistor
  • Simplifying gives: Vout = 2 * V1

• Final Expression:

  • IL = Vin / R
  • Load current (IL) independent of load resistor (RL)

Conclusion

• Summary of how to design voltage to current converter using op-amp
• Encouragement to ask questions or provide suggestions in comments
• Call to action: Like the video and subscribe for more content