#521

Episode 521
70mA output current good for headphone amps or driving LEDs
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[@azav8raa]

As a retired engineering manager, the last thing I wanted to hear from one of my guys was "Interesting" or "funny" when we were in the lab. It usually meant we had a serious issue that had us headed to a product delay. Thanks for the video and i will need to get a couple of the 4556 to try out.

[@colombowala]

at +/- 5V the JRC4556 can drive 32 Ohms, paralleling these with series 2.2 Ohms each at their respective output, one can drive even lower impedance headphones. They are also stable with long headphone cables (capacitive loads due to long wires). CMOY, Objective 2, Grado RA1headphone amp uses these same opamps

[@dalenassar9152]

GREAT video!! Just after watching it, I ordered a few 4556 op amps. When you put a 100 ohm resistor across 10v, that's 1 WATT of power dissipation, which means use a 5 W resistor (which will still get hot). BTW: are you swapping op amps with power ON?

[@IMSAIGuy]

yes I hot swap them all the time

[@ПетровиБоширов-р1ы]

This amplifier is interesting because it has zero output resistance, high output current and low price. This makes it ideal for building a simple but high-quality inexpensive headphone amplifier. However, it is already old and does not seem to be released. Are there now modern similar operational amplifiers "cheap, with zero output impedance and high output current"?

[@IMSAIGuy]

digikey has 3000 in stock: NJM4556AD

[@bayareapianist]

I don't understand the usage of the hi current opamps. Usually there are some driving transisto'rs in power circuits which opamps can offset the gains. I've heard about some power opamps which can drive a few amps. In 80s, there were a bunch of audio amps which looked like power opamps.

[@IMSAIGuy]

some reasons. 1. chip count 2. short circuit protection 3. pcb routing 4. already characterized (spice model) 5. cost? 6. easy

[@EdgarsLS]

The NJM5532 does specify max output current when shorted; 32mA

[@IMSAIGuy]

there is a graph of output voltage vs load resistance in the datasheet.

[@dalenassar9152]

Have you heard of a company called "APED" that sold power components? I can't APEX now. They sold op amps that would put out 10's of Amps!!! I do have one of their fairly cheap PA26 dual op amp that, IIRC, can put out at least couple of amps. They even made some for driving high-current reversible motors.

[@phuocnguyen8774]

I need more current for diy ribbon headphone? please give me your recommend

[@rogerwalter2500]

Parallel these JRC4556 as unity gain with NE 5532 as a gain stage. Use 4.7 R series output resistor for joining outputs of jrc4556 together. Search objective 2 headphones amplifier by nwavguy for more information

[@t1d100]

Thank you.

[@osmanfb1]

what was the frequency you used? I could not see it.

[@IMSAIGuy]

1khz

[@osmanfb1]

@@IMSAIGuy so these unity gain instabilities happen at these low frequencies? I had a notion that maybe these happened at MHz levels. guessed wrong :-(

[@IMSAIGuy]

@@osmanfb1 I don't think what I was seeing was unity gain problems. I was lack of bypass capacitors and long leads and protoboard.