Operational Amplifier Applications Unit 6 – Full-Wave Bridge Driver/Conversion
Exercise 1 – Op Amp Voltage-to-Current Conversion
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the operating
characteristics of an op amp voltage-to-current converter by applying a dc input voltage. You
will verify your results by measuring dc output current.
DISCUSSION
- Op amp (U1) is configured as a noninverting amplifier, has a high gain, and a very high input
impedance. - The op amp output voltage moves up or down to make the voltage drop across R1 (V1) equal
to the input voltage (Vi). Current is generated through the feedback path. - The output current can be adjusted by varying R1 since the voltage drop V1 matches the
input voltage Vi. - The four diodes form the full-wave bridge rectifier. CR2 and CR3 conduct when the input
voltage is negative. CR1 and CR4 conduct when the input voltage is positive. - The full-wave bridge rectifier maintains a one way flow of current through the meter. This
allows ac input voltage and dc input voltage (of either polarity) to be converted. - The calibration resistor (R1) can be used to adjust the circuit to any voltage-to-current factor
(within the circuit limitations). The conversion factor is found using this equation:
FC = Io/Vi - The output current is found using this equation: Io = FC x Vi