Current to Voltage Converter

Calculate current to voltage converter circuits (transimpedance amplifiers). Design photodiode amplifiers, current sensors, and precision current measurement circuits.

Current to Voltage Converter (Transimpedance Amplifier)

                         Rf
    Iin โ”€โ”€โ”ฌโ”€โ”€โ”€โ”€โ”€/\/\/\โ”€โ”€โ”€โ”€โ”€โ”ฌโ”€โ”€โ”€ Vout
          โ”‚               โ”‚
          โ”‚    โ”Œโ”€โ”€โ”€โ”€โ”€โ”    โ”‚
          โ””โ”€โ”€โ”€โ”€โ”ค-    โ”‚    โ”‚
               โ”‚  Op โ”‚โ”€โ”€โ”€โ”€โ”˜
          โ”Œโ”€โ”€โ”€โ”€โ”ค+  Amp
          โ”‚    โ””โ”€โ”€โ”€โ”€โ”€โ”˜
          โ”‚
         GND
         
    Vout = -Iin ร— Rf
    Gain = Rf (Transimpedance Gain in ฮฉ)
mA
mV/mA
MHz
pF

About Current to Voltage Converters

Current to voltage converters (I-V converters or transimpedance amplifiers) convert current signals to voltage signals. They're essential for photodiode amplifiers, current sensing, and precision measurement applications.

Key Characteristics:

  • Virtual Short: Input voltage โ‰ˆ 0V (virtual ground)
  • High Input Impedance: Minimal loading of current source
  • Linear Response: Output proportional to input current
  • Bandwidth Limitation: Gain-bandwidth tradeoff

Design Considerations:

  • Stability: Compensation may be required
  • Noise: Johnson noise from feedback resistor
  • Bandwidth: Limited by feedback capacitance
  • Op-amp Selection: Low input bias current important

Op-amp Recommendations:

  • Low Noise: OPA627, LT1028, AD797
  • High Speed: THS4031, LMH6624, ADA4817
  • Low Bias Current: LMC6001, OPA128, ADA4530
  • General Purpose: TL072, LM358, OPA2134