variable  high current low noise variable converter - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: August 11, 2025, 08:29:51 am
content: Hello , I need to supply several amplifier with 3V 3.3V 5V 10V5V supply is needed for several amplifers in total 500mAIs there some variable high current that can supply 1A (would be great) reference voltage device.I know TL431 its great with variable voltage and low noise but it can only supply at most 100mA.is there a similar stronger device which could be used as negativ and positive variable reference with current at least 1A?Thanks.

author: Terry Bites
author_rank: Super Contributor
timestamp: August 11, 2025, 10:23:31 am
content: Its unlikely that linear regulator noise is going to affect your amplifiers.Firstly its important to stop noise from entering the regulator.I've often used ready made blocks as input filters. eg BNX003-11.Standard 78xx and similar fixed regulators are very quiet. Sub 3nV per root Hz. The bandwith of the amplifier supply is going to be in the mHz.A small resistor (a few ohms) between the regulator output and the supply rail is usually enough to tame this kind of noise. Small R big C of your decoupling caps.Recall that decoupling is effectively a short circuit for AC and noise. Proper decoupling needs to be applied.You can easily boost the current from a TL431.But why not use an adjustable regulator?eg LM317 or adjustable LDO.The TLV761 comes in many output voltage variants, 60uV noise! They will cost less per rail than a boosted TL431.See circuit for TL431. Just about any medium power Darlington will work. You will likely have need a heat sink.

author: john23
author_rank: Frequent Contributor
timestamp: August 11, 2025, 05:28:43 pm
content: Hello Terry,Where Can I see in the datasheet what component name corresponds to whatoutput voltage of TLV761 ?Also Is there a tunable (by resistors) device you reccomend?Thanks.https://www.ti.com/lit/ds/symlink/tlv761.pdf?ts=1754910780560&ref_url=https%253A%252F%252Fwww.google.com%252F

author: Cpuch22
author_rank: Contributor
timestamp: August 12, 2025, 03:12:22 am
content: Check out LDO regulators by TI. TPS7A there are a lot of different options with different current output capabilities input and output voltage ranges and package types.Here is a quick filter from Mouser for TPS7A with adjustable output. I'm not sure what your supply voltage is but I'm guessing 12V or 15V maybe since you need 10V out? You'll need to configure those filters.https://www.mouser.com/c/semiconductors/power-management-ics/voltage-regulators-voltage-controllers/ldo-voltage-regulators/?q=tps7a&number%20of%20outputs=1%20Output&output%20type=Adjustable&polarity=Positive&instock=y

author: Terry Bites
author_rank: Super Contributor
timestamp: August 12, 2025, 08:08:36 am
content: In the datasheet.Page 19.Voltage increments of 100mV!Common output values are easily available egseewww.mouser.co.uk/c/?q=TLV761

author: john23
author_rank: Frequent Contributor
timestamp: August 14, 2025, 08:39:58 am
content: Hello, There is a power consumption consideration.I need to supply in parralel several amplifiers with with total current of 0.54A.I intend to convert 12V input to 5V output so my device has (12-5)*0,5=3.78W threw it.Suppose I will try to use 595-TLV76150DCYRHow can I know that the power which will flow threw this device wont burn it?I have found something that could help shown in the photo below, but I am not sure what number s to use?How do I calculate the expression in my case?Thanks.https://www.mouser.co.uk/ProductDetail/Texas-Instruments/TLV76150DCYR?qs=Jm2GQyTW/bii1Rd2R0M2bQ==https://www.ti.com/lit/ds/symlink/t...l=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTLV761

author: john23
author_rank: Frequent Contributor
timestamp: August 17, 2025, 08:09:39 am
content: Hello , I am building a biasing system for RF amplfiers so I prefer to use regulators with as low noise as possible ,thats why I prefer to use linear regulator and not DC-DC(unless its not possible)So if I look at the LM7805 data sheet delta_T=3.78*62=234C so I think this device would get burned.What do you suggest to do with 7809 so its wont get burned?How the 7809 will help us not getting 7805 getting burned?Thanks.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: August 17, 2025, 09:46:10 am
content: Your own table has your answer.If you want 3+ watts, a SOT223 is not going to cut it, pick a proper package (TO220) and use a heat sink.

author: john23
author_rank: Frequent Contributor
timestamp: August 17, 2025, 10:31:32 am
content: In digikey I get massages that these devices are obselete.Could you reccoemd me a device which I could use?Thanks.