I need help designing an amplifier that is capable of providing 1 W to an 8 Ohm speaker. I have 3.3 V, 5 V or 18 V supply available to power it.
I also have only one power supply available that has no negative output.
The signal is coming from an AVR as a 3.3 V PWM signal. I have following components available:
- NPN, PNP transistors,
- N-channel MOSFETs,
- TL494 Pulse-Width-Modulation Control Circuit,
- JRC4558, LM358 op amps,
- NJM13700 TRANSCONDUCTANCE AMPLIFIER
- and other standard equipment
The last three ICs I got from an old 500W amplifier (thats why I posted them in here if they are useful).
I already experimented with push-pull, common emitter but just couldn't get it to work (not enough power and distortions).
I request this question to be reopened.
I am editing this question with hopes to get help from you guys, I will try to stick to the rules.
Thanks to Olin Lathrop I designed a bridged class D amplifier, but its not working as it should. First off, here is the schematic:
NOT, AND, NAND gates are all made from NAND logic gates.
NOT1 inverts the PWM signal to drive the other half of H-bridge, combined with AND3, and D6 (which is output pin on MCU), they drive the other half of the H-bridge only when D6 is high, preventing it to be on, when PWM output is low.
NAND1 prevents both halves of the H-bridge to be on at the same time (at least thats what I though it would do).
NAND1, AND1 drives one half of the H-bridge, when the PWM signal is high.
NAND1, AND2 drives second half of the H-bridge, when the PWM signal is low.
The purpose of these logic gates is also, to convert 3.3 V PWM signal to 5 V.
If I connect only one half of the H-bridge I get expected distorted sound output. Now, when I connect the second half, it makes a really bad noise and PWM signal stops.
What I think happens:
When I did some measurements with osciloscope I expected that when I would add(+) both waveforms, from AND1 and AND2, I would get a flat +5 V line, but in reality there are some spikes reaching to 0 V and 10 V on both rising and falling edges of the waveforms. So I suspect that, due to this, both of the halves of the H-bridge are on for a small amount of time, to short circuit whole thing to ground.
I am not an expert on this matter, so I would really appreciate any help from you.