LM324 push/pull ckt?

Output to ground is best... low enough value forces it into NPN-only class-A. R to plus gets a lousy PNP involved.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |

I hope by audio, you mean something that tops out at 3000 Hz, like telephone voice.. The LM324 isn't fast or low distortion enough to keep up with much more. But This might work.

+5 | +-------------R2---+ R3 | | |

---C1-R1------+-|+ /-|-+-R4-+ | >-+--2k--< | | +-|-/ | +|------+--+ | | | | +------+ R5 C2 | | 0v 0v

R1 is there to reduce the 5 volt swing to 3.5 volts, so the gain 1 amp does not clip. R2=R4 for gain=-1. R3 and R5 bias both amps at a bias point of about 1.75 volts.

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John Popelish

Oops, just caught the 6 volt supply spec. That helps a lot.

+6 | +-------------R2---+ R3 | | | ---C1-R1------+-|+ /-|-+-R4-+ | >-+--2k--< | | +-|-/ | +|------+--+ | | | | +------+ R5 C2 | | 0v 0v R1 is there to reduce the 5 volt swing to 4.5 volts, so the gain 1 amp does not clip. R2=R4 for gain=-1. R3 and R5 bias both amps at a bias point of about 2.25 volts.

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John Popelish

Firstly, I think you probably mean a differential or 'balanced' output.

5V rms ? 5V pk-pk ? 5V pk ?

You'll get sod all voltage swing out of an LM324 running on a single 6V supply !

Why a shitty LM324 ? Why 6 Volts ?

Probably because it would be expected that anyone wishing to do anything so basic would have a clue to begin with ?

First off you need to explain what you require accurately and concisely. If you can't do that you're probably better off forgetting it !

Graham

Maybe 680 ohms to +6. But that will kill a bit of the negative swing.

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John Popelish

Agreed. But you get a bigger swing with the pull up.

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John Popelish

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>          '-'       '-'         |  ===     ===              |  | |

yep, lm324, ugh. if its for audio try AD's ssm2142 diff line driver

martin

Serious error. All shortcuts have disappeared. Screen. Mind. Both are blank.

While seconding the above, if you're going to have to try something (you're on a desert island with an internet link, a tube of LM324s and a bunch of passive components), you might as well try this (view in fixed font or M$ Notepad):

+6V | 10K +6V .-. .---------. ___ | 15K| | | | .-|___|-. .-. | | | | | | 1500| | '-' | +6V | | | 10K | | 100uF | | || | Load | /| | ___ '-' Input Audio | '--|- | ___ | /-|-o-|___|-. | ___ ||+ | | >---o-|___|-o--< | | | o-|___|--o--||-----o-----|+/ | 2K +|-------------o----. 470 | || | |/| | | | | | | | === | | | | .-. .-. GND | | | | | |470 11K| | | | .-. +| | | | | | 1100| | --- '-' '-' | | | | --- | | | | '-'100| === === | | | uF| GND GND '-----------------------' === === GND GND created by Andy´s ASCII-Circuit v1.24.140803 Beta

You'll want to divide down the signal (470 ohm resistors), and then AC couple it to a DC reference voltage of about 2.5V (about half the range of the LM324 output). You then use a voltage follower and an inverting amplifier with a gain of -1 to create your differential output. The total gain will be 1.

There are a _lot_ of limitations with this circuit, and you'll only get near audio (like near beer is to beer, a very disappointing experience). It will kinda-sorta work, in the "speech might even be intelligible if they speak lowly, slowly and clearly" sense. But I don't think you'll get much better with an LM324. Please think about using something else. Digi-Key ships to desert islands, too.

Questions like this usually receive a better reception on sci.engineering.basics.

Good day (in a Paul Harvey kind of way) Chris

I read in sci.electronics.design that CFoley1064 wrote (in ) about 'LM324 push/pull ckt?', on Thu, 16 Dec 2004:

That's an LM324. Doesn't it need 5.6 kohms from each output to ground to prevent crossover distortion?

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Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.

(view in fixed font or M$ Notepad):

+6V | 10K +6V .-. .-------. ___ | 15K| | | | .-|___|-. .-. | | | | | | 1500| | '-' | +6V | | | 10K | | 100uF | | || | Load | /| | ___ '-' Input Audio | '--|- | ___ | /-|-o-|___|-. | ___ ||+ | | >-o---o-|___|-o--< | | | o-|___|--o--||-----o-----|+/ | | 2K | +|-------------o----. 470 | || | |/| | .-. .-. | | | | | | === | | |1K | |1K | | | .-. .-. GND | | | | | | | | | |470 12K| | | '-' '-' | .-. +| | | | | | | | 1200| | --- '-' '-' | === === | | | --- | | | GND GND | '-'100| === === | | | uF| GND GND '---------------------------' === === GND GND created by Andy´s ASCII-Circuit v1.24.140803 Beta

The new DC bias point is a midlle ground between requiring excess current for the new resistors and the maximum output voltage of the LM324 when sourcing current.

Thanks for the spot, Mr. Thompson.

Chris

Can anyone recommend a schematic for a push/pull, or "dual drive", type amplifier (unity gain) based on 2 amps of an LM324 that will drive a 2K resistive load?

Input is 5V audio. Supply is 6V.

Couldn't find anything specific via search.

Thank you,

Robert M.

Sledgehammer to crack a nut ?

I doubt the SSM will like single supply 6V either.

Graham

I recall using that trick with 748s errrr.... about 30 yrs ago ! Fortunately Texas's bifets came along not long after.

Graham

Why not get a TI TLC07x-series rail-to-rail OpAmp? Perfect for your application.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |

Yep, a bit of an overkill, but how about using one or two of the opamps as an oscillator, into a CW multiplier to provide a vcc boostrap?, might be able to get a bit more headroom that way

martin

Serious error. All shortcuts have disappeared. Screen. Mind. Both are blank.

Sorry, Mr. Popelish. The cruddy AOL newsreader has finally caught up with the thread, and I see I stepped over your input. I guess I'm too cheap to subscribe to a store-bought real newsreader. (;-)

The LM324 datasheet does state it's better at sourcing than sinking current. This would make sense, as it's a single supply op amp. That might leave the pullup/pulldown question up in the air a bit.

But you're correct, the inverter --> inverter solution does amplify the distortion of the first amp. My ASCII schematic above definitely isn't elegant. Oh, well. Nobody promised the OP 0.05% THD. Either way, he has enough to work with.

Thanks for the spot. Happy holidays.

Chris

Xnews and Xananews, among others, are freeware and quite good. Get over to

and grab a few, keep the one you like.

- YD.

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