Author Topic: What is the diffrence between lm324 and lm318 opamps  (Read 2349 times)

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Offline elmatadorTopic starter

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What is the diffrence between lm324 and lm318 opamps
« on: May 08, 2019, 01:26:09 pm »
i want to design the same function generator by using lm318 only
 

Offline flynwill

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Re: What is the diffrence between lm324 and lm318 opamps
« Reply #1 on: May 08, 2019, 01:38:21 pm »
I suggest you go read the data sheets.

The LM324 has roughly 10x the bandwidth of the LM318.   The designer likely choose it for the square-wave section to get shorter rise/fall times on the square-wave signal. The circuit should work with all LM318 sections, just won't reach as high a frequency, and will have softer edges on the square-wave signal.
 

Offline Gyro

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Re: What is the diffrence between lm324 and lm318 opamps
« Reply #2 on: May 08, 2019, 04:56:20 pm »
I suggest you go read the data sheets.

The LM324 has roughly 10x the bandwidth of the LM318.   The designer likely choose it for the square-wave section to get shorter rise/fall times on the square-wave signal. The circuit should work with all LM318 sections, just won't reach as high a frequency, and will have softer edges on the square-wave signal.


Completely the wrong way round, the LM318 is a 15MHz 50V/us part (or 150V/us with feedforward compensation). Way faster than an LM324, which only has a unity gain bandwidth of 1MHz.

The LM318 is still unity gain stable though but you would need to be more careful with layout.
Best Regards, Chris
 

Offline Conrad Hoffman

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Re: What is the diffrence between lm324 and lm318 opamps
« Reply #3 on: May 08, 2019, 07:04:27 pm »
The LM318 is a very old part. Still capable, but also very prone to oscillation if you don't do everything right. I'd get some LM324s for that project. They're cheaper and less troublesome.

There are some interesting circuits where the input stage of the LM318 is turned off, and replaced with discretes to get higher performance. Not sure if those circuits haven't been surpassed by more modern parts.
 

Offline David Hess

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Re: What is the diffrence between lm324 and lm318 opamps
« Reply #4 on: May 08, 2019, 09:06:43 pm »
The 318 was one of the first if not the first "video" operational amplifiers.  Input degeneration gives high bandwidth and slew rate but also higher noise and less precision.  There are modern "video" operational amplifiers which use the same idea but also other types of video operational amplifiers.

318 Faster
324 Slower

318 Dual Supply Part
324 Single Supply Part

318 +/-15 Volt Maximum Differential Input Voltage (1)
324 +/-36 Volt Maximum Differential Input Voltage

The modern AD818 is very similar and I suspect intended as an improved replacement although it does not support external compensation and has a different offset null configuration.  Th AD825 is an alternative I would consider because its higher maximum differential input voltage makes it more general purpose.

(1) This matters when used as a comparator.

The LM324 has roughly 10x the bandwidth of the LM318.

You are thinking of the LM308 but even it is not that slow.  An LM308 will actually be faster than an LM324 in most applications when properly frequency compensated.
 


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