run dual supply opamp on single supply - Page 1
Forum section: electronics / beginners

author: Herschel
author_rank: Regular Contributor
timestamp: March 18, 2024, 02:22:58 am
content: is it posible to replace the lm741 opamp with ne5532 or jrc4565?. is there any way to run ne5532 as a gain amp in single supply mode?

author: TimFox
author_rank: Super Contributor
timestamp: March 18, 2024, 02:45:56 am
content: The circuit shown will work with any op amp that includes 12 V total power supply in its operating range.The 5532's recommended total voltage goes down to 10 V.Note that almost no op amps have a power "ground" terminal, just V(neg) and V(pos).https://www.ti.com/lit/ds/symlink/ne5532a.pdf?ts=1710694597827&ref_url=https%253A%252F%252Fwww.google.com%252F

author: wraper
author_rank: Unknown
timestamp: March 18, 2024, 02:59:28 am
content: There are almost no op-amps with dual supply (having +/- and GND connection). None of those you mentioned are dual supply. Dual supply generally means how circuit (op-amp in/out) is referenced, nothing to do with op-amp itself.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: March 18, 2024, 05:29:53 am
content: Quote from: Herschel on March 18, 2024, 02:22:58 amNote that C3 is in the wrong place. It should be moved from where it is shown to between the op-amp output and the output potentiometer. The way it is shown forces a dc current through the pot of about 3 mA which could be avoided.

author: wraper
author_rank: Unknown
timestamp: March 18, 2024, 11:17:20 am
content: Quote from: basinstreetdesign on March 18, 2024, 05:29:53 amIf opamp output stage works in class-B, loading it in this way may decrease distortion.

author: Herschel
author_rank: Regular Contributor
timestamp: March 18, 2024, 01:03:26 pm
content: ok let me try...

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 18, 2024, 01:09:49 pm
content: Moving C3 will also change the filtering characteristic of the output filter. If I assume it's audio, and the output goes into a 20k Ohm load, then the corner frequency will shift a factor of 10, and that is quite significant.With a 2k load it will be:1/(2e3*1e-6*2*pi) = 79.5Hz... and this is a bit high for audio. With the implied 20k it will be 8Hz and that's "plenty" for audio.

author: TimFox
author_rank: Super Contributor
timestamp: March 18, 2024, 03:22:20 pm
content: By the way, the only op amp I remember with a “ground” power pin along with negative and positive power pins is the long-obsolete uA702 that Fairchild introduced in 1964.Its internal circuit is quite different from the 709, 301, and 741 designs that followed it.

author: Herschel
author_rank: Regular Contributor
timestamp: March 19, 2024, 12:23:42 pm
content: it worked pretty well... i replaced the 741 with njm4565, it works fine... but the 2.2 ohm resistor in the output of power amp section started to get really hot, now its half burnt am i supposed to use one with bigger value. why does it get hot first of all? it is connected series with a 0.47uf film capacitor to the ground

author: wraper
author_rank: Unknown
timestamp: March 19, 2024, 12:33:52 pm
content: Quote from: Herschel on March 19, 2024, 12:23:42 pmIt means something is oscillating at high frequency.

author: exe
author_rank: Unknown
timestamp: March 19, 2024, 01:22:00 pm
content: Quote from: Herschel on March 19, 2024, 12:23:42 pmIs there a decoupling capacitor? I don't see it on schematic. I'd place a ceramic one as close to opamp's supply pins as possible.

author: Herschel
author_rank: Regular Contributor
timestamp: March 19, 2024, 03:54:46 pm
content: yeah i know that but what is it?. i think its from the bluetooth module in it. but even after i turned the module of, it still getting hot. is it okay to use a 10 ohm resistor instead of 2.2ohm.

author: Herschel
author_rank: Regular Contributor
timestamp: March 19, 2024, 03:57:16 pm
content: Quote from: exe on March 19, 2024, 01:22:00 pmits not in the circuit but i have already used it

author: Herschel
author_rank: Regular Contributor
timestamp: March 19, 2024, 03:59:08 pm
content: Quote from: Herschel on March 19, 2024, 03:54:46 pmi had also noticed the same when using a tda 2050 amplifier in single supply mode...

author: wraper
author_rank: Unknown
timestamp: March 19, 2024, 05:37:52 pm
content: Quote from: Herschel on March 19, 2024, 03:54:46 pmResistor is not the problem. If it gets hot with no audio, it's 100% sign of your circuit oscillating at high frequency.

author: MarkT
author_rank: Frequent Contributor
timestamp: March 19, 2024, 06:55:40 pm
content: Quote from: Herschel on March 19, 2024, 12:23:42 pmInadequate decoupling, or positive feedback due to stray capacitance. Either can cause HF oscillation, simply swapping opamps without attention to the details is fraught with such dangers. Certainly wise to include a 100nF ceramic capacitor across the supply within 1cm of the NJM4565, maybe add 5 to 10pF between inverting input and output of each opamp.High frequency oscillations passing through the power amp will fry the Zobel network resistor as you have found out. Ironically the Zobel network is to stop the power amp oscillating...

author: Herschel
author_rank: Regular Contributor
timestamp: March 21, 2024, 04:09:52 pm
content: i am soo stupid i was using a jrc2068d instead of jrc4565I noticed this when I decided to rebuilt the circuit to a copper clad... and now its not oscilating(resistor is not getting hot) but the amplifier is making a weird sond on turning on the amp. when i turn it on with a pluged in smart phone nothing happen. is ther any way to prevent that noice?

author: Terry Bites
author_rank: Super Contributor
timestamp: March 21, 2024, 05:25:08 pm
content: Never pass up an opportunity to replace a 741.

author: Herschel
author_rank: Regular Contributor
timestamp: March 22, 2024, 11:09:12 am
content: i have already tried running on it on 741... but the audio is destorted. but it sounds like an audio amp from old times...

author: Herschel
author_rank: Regular Contributor
timestamp: March 22, 2024, 01:58:34 pm
content: GUYS AN EXTREMELY WEIRD NEWS... I have accidentaly created a radio... After replacing the circuit with jrc4565 i changed the 220k resistor in the first circuit to 56k resistor and replaced the 2k preset with 10k according to my needs and after turning it on, the zober resistor started to get little bit warm and the opamp started oscilating.I accidently touched the input capacitor AND I COULD HEAR MY LOCAL RADIO which is tuned to around 101mhz.I think my opamp is oscilating at 101mhz.how to prevent this? i have never seen something like this before... can someone plz explain this?

author: exe
author_rank: Unknown
timestamp: March 24, 2024, 02:19:17 pm
content: I didn't have this myself, but read about it)https://www.quora.com/Why-does-my-OP-amp-pick-up-radio-channelsThough I'm surprised it detects FM-modulated signal. Solution? May be shorter input leads and rf-filtering? Like, a ferrite bead and a capacitor. Some opamps have RF-filters (in a form of RC-filter at the input, I guess). Some reading about this:https://www.ti.com/lit/an/sboa128a/sboa128a.pdf

author: Herschel
author_rank: Regular Contributor
timestamp: March 26, 2024, 05:38:11 pm
content: i dont know really what happend, i forgot to take a video of it happening, sadly, the next day, it stopped doing that. So i was not able to check it. but still weird though...

author: Vovk_Z
author_rank: Super Contributor
timestamp: March 26, 2024, 07:57:01 pm
content: Proper decoupling and proper wiring often helps. If not then additional capacitors in feedback which make frequency range more narrow.

author: Herschel
author_rank: Regular Contributor
timestamp: March 27, 2024, 02:09:53 pm
content: i have already corrected it. Now everything is working fine...