Come & get yer watts!!!

I've been doinking around with some simple amplifier circuits, and I've discovered that increasing the load resistor value reduces the current through the transistor, thus increasing the voltage gain, while reducing current gain. And, of course, reducing the load resistor produces just the opposite effect. This got me thinking.... ( Stand back - this could get messy! ) What's the "best" voltage or current for a given circuit? I suppose it depends what type of device you're trying to drive, ( loudspeaker, motor, led, etc...) but if that's true, then who's hungry for voltage & who wants current? This thing's got me so befuddled, I'm not sure which way's down! Ideas, anyone?

 

Thanks, Duke37, for the valuable info! The power source in this case is a simple 9v "transistor" battery - I like to work with low voltages, so that when ( not "if" ) I screw something up, I generally don't fry my components. ( much less myself! ) I guess what I was hoping to figure out was a general rule of thumb for various types of devices. For instance, if I'm trying to drive an LED or a motor, I can just look at the spec sheets for those items to see what each requires, however for a speaker, it gets a bit more fuzzy - often small, cheap speakers are marked in terms of impedence, but they rarely show max power ratings. I know that it's important to match impedences when dealing with speakers, but if a particular speaker requires a low impedence ( say, 8 ohms ), how might that effect the voltage gain of the transistor? Thanks again, for the input - all info is appreciated!

 

Howdy, BobK! Thanks for the reply! The circuits I've worked with thus far are simple single-stage audio amps ( although, I suppose they'd probably qualify as pre-amps ), consisting of a single 2n2222 transistor & a handful of components. I guess, technically, they'd be called Class A, Common Emitter amplifier circuits and, yes, the "load" resistor I referred to is on the collector. I'm familiar with the push-pull configuration, but I'm more interested in a single-ended output stage, perhaps a darlington transistor? Basically, I am attempting to build a simple, reliable pre-amp stage for musical circuits, such as oscillators, active filters, guitar distortion pedals and such. So, I suppose line-level signals would be sufficient for coupling to further processing circuitry, though perhaps enough gain to drive a pair of headphones would be useful.

 

Thanks for the link, AnalogKid! (Awesome tune, by the way!) I will definitely check that out - Wikipedia's got SO much helpful information!

 

Thanks, Ratch, for replying - as I mentioned in another post, I'm attempting to build a simple pre-amp stage for various musical circuitry; oscillators, active filters, distortion pedals and such. But, moreover, I'm just trying to get a handle on which types of devices (on average) require what type of power; for instance, are loudspeakers current-hungry, or voltage-hungry? Same for motors, LED's, transistors, etc..... I realize, of course, that every specific device has it's own requirements, but I'm just wondering if there are general "trends" for given device types.

 

If I haven't already said it, Thanks, all, for such prompt and helpful input! It's encouraging to see a forum so active and lively, and your interest in my conundrum is greatly appreciated!