# Troubleshoot a bipolar amplifier circuit

I am working on a project in which I am attempting to interface with an ILDA galvanometer from an arduino to move around a projected laser beam. I am following a guide linked here, particularly step 7 at the introduction of the amplifier circuit.

If I understand the logic correctly, the desired function of this amplifier is to take an input of 0-4V on line 2 (driven by the arduino and a DAC) and output a 5V+- signal on lines 1 and 7, following the following relation:

• Input 2 = 0V, Output 1 = -5V, 7 = +5V
• Input 2 = 1V, Output 1 = -2.5V, 7 = +2.5V
• Input 2 = 2V, Output 1 = 7 = 0V

and so on. This circuit is giving me trouble as I don’t particularly understand why it is designed as such, not having much experience in the realm of EE myself. More so, I have run into problems attempting to build it on a breadboard myself, resulting in the following incorrect outputs on wires 1 and 7.

• Input 2 = 0V, Output 1 = 0V, 7 = 0V
• Input 2 = 4V, Output 1 = 3.9V, 7 = 3.5V

I am not sure if this is a problem with my implementation of the circuit, or a flaw with the circuits design. Any intuition as to what could be wrong with either one, and how to test and troubleshoot would be much appreciated!

• Your schematic doesn't show the inputs and outputs you mention in your words rendering the schematic you have shown useless. Where is Input 1 also? Dec 5, 2020 at 11:09