LM324 - Electronic Circuits Projects Diagrams Free

Dr.EM · 25th March 2006, 03:28 PM

Hi. I was wondering how similar the LM324 was to the 741. I have a breadboarded circuit made with 741 and 1458 chips and those work fine for it, but when I make it as a unit I intend to use some quad op-amps to save space and connecting up lots of power rails. I found that some of my 071 chips oscillated and I couldn't seem to control with any method (supply rail caps, small cap in feedback loops, resistors on output). So i'm specifically looking for a low bandwaidth quad op-amp, in this list:

http://www.rapidelectronics.co.uk/rk...4443&XPAGENO=1

Noise is not an issue as its dealing with large voltages, and the absolute maximum frequency is 20khz (usually well below that, this is a low frequency muliple waveform oscillator). Thanks.

audioguru · 25th March 2006, 03:48 PM

If you keep the output level low, the poor high frequency response of the 741 and M324 old opamps won't matter much.

Dr.EM · 25th March 2006, 04:30 PM

Looking at those graphs it would seem the LM324 is quite similar to the 741 (slightly slower even), certainly not on op-amp that will oscillate, so its probably a good alternative. No problems with using it as an alternative? functions used including low gain inverting amps, summing amps, schmitt trigger and ramp generators.

audioguru · 25th March 2006, 04:42 PM

Quote:

Originally Posted by Dr.EM

Looking at those graphs it would seem the LM324 is quite similar to the 741... No problems with using it as an alternative?

The LM324 is the industry's first "low power" opamp so they made the output transistors without bias current. Therefore they produce horrible crossover distortion with audio signals unless you bias an output transistor with a DC load as a class-A amplifier.

Dr.EM · 25th March 2006, 04:52 PM

That sounds bad...

I see there is an LM324, and an LM324N, which is specifically labelled low power, but you say they both are? There isn't a quad 741 is there?

**Nigel Goodwin** · 25th March 2006, 05:24 PM

Quote:

Originally Posted by Dr.EM

That sounds bad...

I see there is an LM324, and an LM324N, which is specifically labelled low power, but you say they both are? There isn't a quad 741 is there?

The LM324 is used in a great many guitar and PA amps, it's perfectly fine for what you want - and is usually considered as a quad 741.

The negative feedback you apply to the circuit sorts the crossover distortion out!.

audioguru · 25th March 2006, 06:23 PM

Quote:

Originally Posted by Nigel Goodwin

The LM324 is used in a great many guitar and PA amps, it's perfectly fine for what you want - and is usually considered as a quad 741.

The negative feedback you apply to the circuit sorts the crossover distortion out!.

The LM324 produces an annoying buzzing 0.3% crossover distortion when it has NO gain, when all its gain is used as negative feedback to try to reduce its crossover distortion. The distortion is much worse when it has some gain.
The datasheet for the LM324 shows how to add a DC load to its output to bias one of its output transistors into operating in class-A for low distortion.

Dr.EM · 25th March 2006, 08:59 PM

Getting a bit of a mixed response :lol:

I think i'll just use 1458s, unfortunately out of stock at the moment. Or 074s, if I could stop them oscillating somehow, whats the standard way? 0.1uF ceramic caps between +v and -v, or 2, one from +v to gnd,another from gnd to -v? Niether of those seemed to work on an 071 set up as a buffer.

audioguru · 26th March 2006, 10:13 AM

Hi Dr. Em,
I have used thousands of Texas Instruments' TL07x opamps in circuits and they don't oscillate. Only the very 1st one I ever used oscillated that was feeding a shielded cable without a 100 ohm resistor in series with its output to the high capacitance to ground of the cable. Japan New Radio (JNR) copied the opamps and they all oscillated.
Please post your oscillating circuit for us to see what is wrong with it.

**Nigel Goodwin** · 26th March 2006, 10:36 AM

Quote:

Originally Posted by audioguru

Hi Dr. Em,
I have used thousands of Texas Instruments' TL07x opamps in circuits and they don't oscillate. Only the very 1st one I ever used oscillated that was feeding a shielded cable without a 100 ohm resistor in series with its output to the high capacitance to ground of the cable. Japan New Radio (JNR) copied the opamps and they all oscillated.
Please post your oscillating circuit for us to see what is wrong with it.

I agree, TL07x's don't oscillate without good reason, it sounds like you're doing something wrong?.

Dr.EM · 26th March 2006, 06:29 PM

Ok, i've changed all the op-amps for 071/072 chips and they seem to be working. It was just the output buffer that was oscillating, but there was some unshielded cable connected to that, so mabye thats why. Another had periodic oscillations on the waveform, but this was tamed with a 10pF in the feedback. So it looks like 074s will be ok, but i'll stick with 741 for the output buffer (the high slew rate of the 071 will probably cause some pops in the speaker on square waves anyhow)

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25th March 2006, 03:28 PM	(permalink)
Dr.EM	LM324 Hi. I was wondering how similar the LM324 was to the 741. I have a breadboarded circuit made with 741 and 1458 chips and those work fine for it, but when I make it as a unit I intend to use some quad op-amps to save space and connecting up lots of power rails. I found that some of my 071 chips oscillated and I couldn't seem to control with any method (supply rail caps, small cap in feedback loops, resistors on output). So i'm specifically looking for a low bandwaidth quad op-amp, in this list: http://www.rapidelectronics.co.uk/rk...4443&XPAGENO=1 Noise is not an issue as its dealing with large voltages, and the absolute maximum frequency is 20khz (usually well below that, this is a low frequency muliple waveform oscillator). Thanks. __________________ Angry!? I'm absolutely electrolytic! Will have to make do with myspace now I guess...

25th March 2006, 04:30 PM	(permalink)
Dr.EM	Looking at those graphs it would seem the LM324 is quite similar to the 741 (slightly slower even), certainly not on op-amp that will oscillate, so its probably a good alternative. No problems with using it as an alternative? functions used including low gain inverting amps, summing amps, schmitt trigger and ramp generators. __________________ Angry!? I'm absolutely electrolytic! Will have to make do with myspace now I guess...

25th March 2006, 04:52 PM	(permalink)
Dr.EM	That sounds bad... I see there is an LM324, and an LM324N, which is specifically labelled low power, but you say they both are? There isn't a quad 741 is there? __________________ Angry!? I'm absolutely electrolytic! Will have to make do with myspace now I guess...

25th March 2006, 08:59 PM	(permalink)
Dr.EM	Getting a bit of a mixed response :lol: I think i'll just use 1458s, unfortunately out of stock at the moment. Or 074s, if I could stop them oscillating somehow, whats the standard way? 0.1uF ceramic caps between +v and -v, or 2, one from +v to gnd,another from gnd to -v? Niether of those seemed to work on an 071 set up as a buffer. __________________ Angry!? I'm absolutely electrolytic! Will have to make do with myspace now I guess...

26th March 2006, 10:13 AM	(permalink)
audioguru	Hi Dr. Em, I have used thousands of Texas Instruments' TL07x opamps in circuits and they don't oscillate. Only the very 1st one I ever used oscillated that was feeding a shielded cable without a 100 ohm resistor in series with its output to the high capacitance to ground of the cable. Japan New Radio (JNR) copied the opamps and they all oscillated. Please post your oscillating circuit for us to see what is wrong with it. __________________ Uncle $crooge

26th March 2006, 06:29 PM	(permalink)
Dr.EM	Ok, i've changed all the op-amps for 071/072 chips and they seem to be working. It was just the output buffer that was oscillating, but there was some unshielded cable connected to that, so mabye thats why. Another had periodic oscillations on the waveform, but this was tamed with a 10pF in the feedback. So it looks like 074s will be ok, but i'll stick with 741 for the output buffer (the high slew rate of the 071 will probably cause some pops in the speaker on square waves anyhow) __________________ Angry!? I'm absolutely electrolytic! Will have to make do with myspace now I guess...