TLE2426 voltage splitter for Amp Op power ? easy and reliable solution ? - Page 1
Forum section: electronics / projects

author: Overspeed
author_rank: Frequent Contributor
timestamp: August 29, 2024, 07:59:37 am
content: HelloOn the Hoffman null meter he use a TL2426 splitter to power the LT1050 ( +/- 4.5 V) from a 9V bateryAs the out current is 20mA max that OK but regarding the noise ?Question : does this setup is reliable or just an easy / cheap solution as the TL2426 handle 40V input max so can be a solution to power +/- 6V from a 12V lead battery or 4x lithium 18650 and the 8 pin DIP allow a cap to reduce noise ?RegardsOS

author: Overspeed
author_rank: Frequent Contributor
timestamp: August 30, 2024, 08:38:50 am
content: HelloAny advise ? as Lt1050 is a precision amp op and a null meter is a supposed high precision equipment so does the TLE2426 is enough or does that could be interesting to go to another solution ?RegardsOS

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: August 30, 2024, 08:58:52 am
content: Hi Overspeed,looks okay to me.And you can always use pin-8 (Noise-reduction) if you're worried aboutnoise on the supply-rails and additional regulators.Where should the noise come from? The battery?Good luckP.S.: A Null-detector is not a Null-Voltmeter.

author: Andree Henkel
author_rank: Regular Contributor
timestamp: August 30, 2024, 09:03:19 am
content: Should be good enough, any noise out of TLE2426 at low frequency will be filtered by the PSRR of the LTC2050.At higher frequency the PSRR drops, but your needle can´t follow anyway.It may not matter, but I don´t see any decoupling cap.

author: Andree Henkel
author_rank: Regular Contributor
timestamp: August 30, 2024, 09:28:00 am
content: I used TLE2425 and TLE2426 in past for both a low power battery powered precision Voltage Source and precision Current Source, it worked just fine.

author: Overspeed
author_rank: Frequent Contributor
timestamp: August 30, 2024, 10:15:25 am
content: HelloThanks for the answer as make a pcb is time consuming and lock valid information is crucial , symmetrical power for amp op is not an easy thing from poor LM78/79 to Traco module to complex circuit.RegardsOS

author: ArdWar
author_rank: Frequent Contributor
timestamp: August 30, 2024, 10:31:39 am
content: I doubt you'll have any problem with noise in practice.But if you're *that* concerned then it's probably good idea to add DNP alternative in your PCB for the usual opamp and two resistor solution.That way you can experiment with many selection of low noise opamps, although you may ends up trading your noise problem with stability problem instead...

author: ivo
author_rank: Regular Contributor
timestamp: August 30, 2024, 11:42:05 am
content: IIRC Conrad has said that he used that part as it was comparatively, common and cheap at the time he designed this (a few decades ago?), and worked for the job.Nowadays it may in fact be cheaper to use simply a better opamp (noise, rejection, power use) with two high value dividing resistors to set a midpoint, than buying the TLE2426, because it is no longer comparatively as cheap. However you also need to know enough about your design so that whatever design do you can handle any capacitive loading on its output. Last time I designed this circuit, and I added capacitors for all the rails, which I blindly thought was good to dampen noise. Turns out I created some nice ringing until I dropped my rail caps by two orders of magnitude (probably still there, but dampens to nothing at DC).If you are using the nullmeter properly there should be extremely little current output required...It's also possible to instead of going with >=9V compatible parts, instead use 5-6V compatible CMOS parts with suitable different power supply (5V LDO regulator, or 6V worth of batteries with a protection diode come to mind). You open up some different options for opamps then, with maybe some better specs than the LCT1050, although that part will still do the job just fine.For an alternative scheme also seeGyro's picoammeter designwhich has a lot of the same elements to this one. Virtual ground scheme and one schmic opamp doing a high gain amplification.Noise on the circuit ground is also coming through 2-3M resistors worth of Johnson noise. As Andree says, a "wobbling ground line" can also be alternatively and equivalently viewed as the positive and negative supplies wobbling together by half as much instead, and thereby the opamp PSRR will reduce those.