Hi
I am currently trying to build an amplifier circuit in a BTL configuration to drive a stepper motor. Before I am connecting it to an inductive load I have been trying to test the circuit with a normal resistive load to ensure it is working as expected. My problem at the moment is that the output on amplifier A is basically dead (following the input), but the output on amplifier B is working as expected. I have used the bridge example circuit in the LM4766 datasheet and I have tried to look on the forums to see if people might have struggled with a similar problem, but could not find any.
My first question: Does the mute time constant have to be larger than a certain amount to ensure the mute is turned off? My time constant is 1.65ms at the moment (using a 5k ohm resistor and a 330nF cap)? Is that too low? I am definitely pulling more than 1mA through those pins and have tested both outputs in a non-inverting manner to ensure that the output/chip is still working. I am just not sure if I am missing something when I connect one side to make an inverting amplifier and if that would somehow affect something in that circuit that might cause the output to be responding incorrectly.
The output of amplifier A looks like it is clipping to my negative supply voltage Vee. (I am using a +- 15V supply voltage for testing purpose at the moment). I tried to see if I have not shorted anything, but I am fairly positive that the connections are correct.
Do you maybe have anything else I can look at or a different design circuit I could try or am I missing something? I could get the amplifiers to work when I connect them separately in a non-inverting connection but as soon as I combine them in BTL connection I am having problems with the one output (the one connected as an inverting op-amp connection).
Thanks in advance for the help.
Kind Regards
Nardus