I want to generate a low freq movement for this loud speaker coil by using a function generator sine output. With the function generator I can generate a sine wave between 0.2Hz up to 100Hz with amplitude up to 2Vpp which is enough for my purpose. I want the coil move between 0.2Hz up to 100Hz.

But the thing is the loud speaker coils passes high currents. So this could be done by a big expensive audio amplifier with many stages. In my case I'm not interested in audio quality noise ect. but just the crude movement of the coil.

60 W 8 Ohm are the specs for the speaker.

I think that means at 60W the coil will pass from the formula P = I^2 x R --> I = 2.7 Ampere rms current which for a sinusoidal wave a sine with +/-3.8 Ampere amplitude.

Can a single push pull stage like shown here with two power MOSFET work for the purpose? If I'm in correct path, what MOSFET parameters should I look into?


You might want to look into using monolithic Class-D Audio Amplifiers for this.

I am not an audio person but there are a few things you need to look out for from a power electronics perspective.

If you pass a sinewave to the gates of your FETs, you're not going to get the same sinusoud out because the FETs wont switch on properly.

You will also need to modulate your sinusoud into a PWM signal suitable for driving the FETs quickly. At this point you will need to add an LC filter to the output to create the sinusoid back from the PWM Pulses.

Shoothrough will also be a concern in a totem-pole output like this where if both FETs are switched in at the same time then you will experience a short to ground which may destroy your FETs and distort the output. Your PWM logic should include deadtime in order to prevent this.

Unless you're interested in building this all from scratch, I would pick up an audio IC to do all this.

If you don't care about efficiency too much, and want to save yourself a bit of pain, a Class-B amplifier might be easier to implement.

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  • \$\begingroup\$ Thanks, I see the challenge, I also need through hole pins. So far I came up with this IC: docs.rs-online.com/8039/0900766b80a333ea.pdf might work for this case. But from its datasheet can we say that this can work with +/-12V supply and run the 8 Ohm 60 W speaker coil without need for heatsink? \$\endgroup\$ – GNZ Mar 19 at 12:17

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