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Old 26th March 2011, 08:44 AM   #1
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Default Need help choosing level shift and inverter

So me and my mate are almost done building our neat little class d amplifier. We have the gate driver part left, well a part of it. First, I've been trying to find some info on what to use to use as a level shift. I've found that a transfomer seems good, or is there any better option, the fiber optic solution would be cool but a bit complicated and expensive.

And second. An op amp to invert the signal? We're intending to use 2 n transistors thus we need to invert the positive signal going through the upper transistor, but I guess you're already familiar with this. I know that V/ns is a good way to indicate how fast it is, but what does rise, fall time and slew rate do? Bit hard to find and understand info regarding these. A better choice to invert the signal? The signal will be 15V maximum with a max of 300 kHz. I'm sure I missed some vital information. Very thankful for help!
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Old 26th March 2011, 11:33 PM   #2
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I used a simple transistor circuit to translate the levels to 0/15v.
I then put the signal into two XOR (4017) gates one wired to buffer and the other wired to invert.

You might need to put a diode from the mosfet gates back to the driver so it turns off quicker than it turns in to stop shoot through (shorting of power supply)
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Old 27th March 2011, 09:31 AM   #3
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Quote:
Originally Posted by nigelwright7557 View Post
I used a simple transistor circuit to translate the levels to 0/15v.
I then put the signal into two XOR (4017) gates one wired to buffer and the other wired to invert.

You might need to put a diode from the mosfet gates back to the driver so it turns off quicker than it turns in to stop shoot through (shorting of power supply)
I don't really understand what you mean. The pulses for my upper transistor first needs to be inverted, and also level shifted so the transistor will "lead" during the full pulse. I've read that it's best to use either a transformer or a diode and capacitor to level shift to the appropriate level. The lower transistor will have no problem leading. Thanks for the info on using xor gates as inverter and buffer. Only level shift left.

Last edited by levelshift; 27th March 2011 at 09:35 AM.
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Old 27th March 2011, 10:30 AM   #4
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Ever heard of IR2xxx ?
Transformer won't do.
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Old 27th March 2011, 05:47 PM   #5
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Originally Posted by darkfenriz View Post
Ever heard of IR2xxx ?
Transformer won't do.
I'm a noob, can you please explain.
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