Evening all!
Bit of a stuck moment;
I'm trying to get an op-amp speaker amplifier up and going, and I have a circuit all drawn up, (see photo below!) and I'm curious on what op-amp I should use for this. It's mainly going to be a 5" subwoofer amp, and possibly more channels. I'm also not ENTIRELY sure wether or not this design would work, but for the circuit, I just put a 30Hz and a 1kHz test load. But a last question before I head to bed, is this circuit ANY good?
Any help is GREATLY appreciated!
Cheers!
Jeff
Why don't you build something complete, tested and functional like this and its way cooler in many many ways than a standard PWM modulator.
http://www.nxp.com/documents/user_manual/UM10155.pdfIts cool cause you will learn everything in once place.
The incomplete circuit you showing is a simple PWM modulator using a triangle sawtooth ramp a high gain amplifier in most cases its a high speed comparator a least you can use is a LM311 or better LM319,using an op amp is straight textbook (and sometimes used in bad designs) and not suitable as its not truly a 1-bit (zero or one) quantizer, anyway this is class-d I had so many debates around this topic with some trolling fool I don't have the energy to extend my help, just for now.
Comparators are not required to operate in closed loop, thus they don't require any internal frequency compensation (at the expense of reduced slew rate). Also, op-amps may have higher open-loop gain at low frequencies, but comparators have higher gain at high frequencies, due to the absence of compensation.
As it has been mentioned, op-amps have evolved a lot in the past decades and hundreds of new models have appeared as opposed to what happened with comparators, but these facts are quite easy to understand. Lets take a LM393 dual comparator and a uA741 dual op-amp as a reference, both are very old devices from 1970s, but while the op-amp is very slow and too noisy for most today's applications, the comparator is fast and is still fine for new designs (my LM393 are swinging from rail to rail in 200ns or so provided adequate input overdrive and output bias).
Don't underestimate devices just for being old. There is still a lot of old stuff regarded as industry standard because it still fits today's needs quite well. Personally, I use a lot of LM393, CD4000 CMOS gates, TL431, BC546/556, BD139/140, LM358, 1N4007, 1N4148 etc... and I like these devices.
PD. Using op-amps as comparators works but produces poor performance.
Source from.
http://www.diyaudio.com/forums/solid-state/71430-comparator-vs-opamp-pros-cons.htmlGood luck.