Bidirectional voltage-to-current converter

Question

How to make the following voltage-to-current converter bidirectional, so that bidirectional current can be driven through the load?

Answer 1

For bi-directional current use an H-bridge.

Use your voltage-to-current converter as current-source drivers instead of the conventional voltage sources.

Something like this:

^{simulate this circuit – Schematic created using CircuitLab}

This works similarly to your circuit, except now you have direction control. Tie the two "DIR CTRL" lines high to turn off. Pull one low for current in one direction, pull the other low for the opposite.

Answer 2

A bidirectional current source can be as simple as an amplifier that can provide both positive and negative outputs then sensing the current with a resistor in the grounded side of the load (similar to the OP design). The sense voltage is then feedback to the opamp.

This circuit requires that both terminals of the load are available. ie the load is floating. If one did eof the load is grounded the classic Howland current pump is a common solution.

To provide currents higher than available from a normal opamp a common solution is to use a push-pull buffer stage consisting of a PNP and an NPN transistor (could also be done with An N-channel and P-channel MSFET although biasing is more tricky).

^{simulate this circuit – Schematic created using CircuitLab}