I have an electromagnet (coil with about 500 uH inductance and 0.8 Ohm resistance) that I want to drive at 4 kHz with about 3 Amps of current. I want to achieve this with minimum noise and power at any frequency other than 4 kHz.
I am using a waveform generator (Stanford Research Systems DS345) to generate a 4 kHz sine wave (unbalanced signal), which is then sent to an audio amplifier (Crown xls 402). The output of the amplifier is a balanced signal connected to the coil. In parallel with the coil I have two zener diodes for flyback to prevent damage to the amplifier in the event of a power failure.
In order to minimize noise coming from the waveform generator or the amplifier, which of the following is optimal? The most critical noise frequencies that I must minimize are those at low frequencies (< 4kHz and in particular those less than 200 Hz) and those over 4 MHz.
(i) Maximize the voltage coming from the waveform generator (10 V peak to peak). Then set the gain on the amplifier to get desired output current
(ii) Set gain on amplifier to maximum, and then set the waveform amplitude to get desired output current
(iii) Something else entirely