Author Topic: What's your opamp dual supply from single supply jellybean solution?  (Read 1779 times)

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Online ArdWar

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Re: What's your opamp dual supply from single supply jellybean solution?
« Reply #25 on: September 22, 2024, 03:05:02 am »
I feel 7660-style charge pumps are in the once great solution but now getting too expensive for what they offer. Today you can pick random cheap buck converter, wire it in inverting mode, and still end up with cheaper BOM and higher current capacity.

Maybe if you already have something that oscillate in your circuit (free MCU pin, another DCDC, etc) you can build your own charge pump for "free".
 
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Offline Thomas

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Re: What's your opamp dual supply from single supply jellybean solution?
« Reply #26 on: September 23, 2024, 11:06:08 am »
LM2766 is a good one: https://www.digikey.com/en/products/detail/texas-instruments/LM2766M6X-NOPB/2514776
More modern (?) and better than the 7660:
2.7 - 5.5V
200mA
2MHz
$1.12 in single quantities
 

Offline dusanTopic starter

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Re: What's your opamp dual supply from single supply jellybean solution?
« Reply #27 on: September 23, 2024, 08:41:39 pm »
LM2766 is a good one: https://www.digikey.com/en/products/detail/texas-instruments/LM2766M6X-NOPB/2514776
More modern (?) and better than the 7660:
2.7 - 5.5V
200mA
2MHz
$1.12 in single quantities

But that doesn't create negative voltage only doubles input voltage.
 

Offline PCB.Wiz

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Re: What's your opamp dual supply from single supply jellybean solution?
« Reply #28 on: September 23, 2024, 09:12:41 pm »
But that doesn't create negative voltage only doubles input voltage.
Correct.
The cheapest way to get modest +/- OpAmp supplies is to use a x3232 (3v3-5V) or x232 (5V) UART transceiver, lcsc have those from as low as ~10c/500+

 

Offline jasonRF

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Re: What's your opamp dual supply from single supply jellybean solution?
« Reply #29 on: September 24, 2024, 12:18:04 am »
 If I don’t need to get down to DC (eg when doing audio) then I often don’t bother.  I just use input and output caps, such as in figure 1 or 2 of

https://www.analog.com/en/resources/analog-dialogue/articles/avoiding-op-amp-instability-problems.html

Especially when I just need a buffer so there is no extra cap required for the feedback. 
« Last Edit: September 24, 2024, 12:21:43 am by jasonRF »
 
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Offline Thomas

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Offline Zero999

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Re: What's your opamp dual supply from single supply jellybean solution?
« Reply #31 on: September 25, 2024, 12:14:20 pm »
I generally avoid it. Most of the time a dual supply isn't necessary. If it's audio, then go with AC coupled, single supply. If it's DC, then level shift and use differential outputs. That will enable you to have positive and negative input/outputs without a bipolar PSU.

Here's an example of a Howland current source I designed to drive a valve with +/-7.5mA, using a +/-10V control signal, yet runs from a single 12V power supply.
« Last Edit: September 25, 2024, 05:13:05 pm by Zero999 »
 


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