Input Voltage (V)

0

0.5

1

1.5

0

0.025

0.05

0.1

Load

0.075

2

D001

21

OPA189, OPA2189, OPA4189

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SBOS830 – JUNE 2017

Product Folder Links: OPA189 OPA2189 OPA4189

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Typical Applications (continued)

9.2.1.1 Design Requirements

The design requirements are:

•

Supply voltage: 5 V dc

•

Input: 0 V to 2 V dc

•

Output: 0 mA to 100 mA dc

9.2.1.2 Detailed Design Procedure

flows through the first stage of the design. The current gain from the first stage to the second stage is based on

For a successful design, pay close attention to the dc characteristics of the operational amplifier chosen for the

application. To meet the performance goals, this application benefits from an operational amplifier with low offset

voltage, low temperature drift, and rail-to-rail output. The OPAx189 CMOS operational amplifier is a high-

precision, ultra-low offset, ultra-low drift amplifier, optimized for low-voltage, single-supply operation, with an

output swing to within 15 mV of the positive rail. The OPAx189 family uses chopping techniques to provide low

initial offset voltage and near-zero drift over time and temperature. Low offset voltage and low drift reduce the

offset error in the system, making this family appropriate for precise dc control. The rail-to-rail output stage of the

OPAx189 makes sure that the output swing of the operational amplifier is able to fully control the gate of the

MOSFET devices within the supply rails.

A detailed error analysis, design procedure, and additional measured results are given in reference design

TIPD102, which is a step-by-step process to design a High-Side Voltage-to-Current (V-I) Converter.

For step-by-step design procedure, circuit schematics, bill of materials, PCB files, simulation results, and test

results, refer to TI Precision Design TIPD102, High-Side Voltage-to-Current (V-I) Converter (SLAU502).

9.2.1.3 Application Curves

Figure 11 shows the measured transfer function for the high-side voltage-to-current converter shown in

Figure 10 .

Figure 11. Measured Transfer Function for High-Side V-I Converter