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Constant Current Source (CCS) For Audio Applications
Constant Current Source (CCS) For Audio Applications
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Old 20th September 2017, 08:08 AM   #61
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Elvee View Post
This is not really a two-terminal CCS, unless you are ready to accept unpleasant tradeoffs.
Here are some examples of 2 wire CCS, some of which can be designed with a -0.3%/C tempco:
Improved 2W current sources (II)
Elvee,
I have posted a couple of questions in your old Thread.
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Old 20th September 2017, 01:09 PM   #62
Mark Johnson is offline Mark Johnson  United States
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Constant Current Source (CCS) For Audio Applications
[LM334 makes quite a nice 5.5 mA current source, works down to 2.0-2.2 volts

Includes measured Current-vs-Voltage plot of two-terminal (floating) current source.

For 250 volt operation, replace the JFET with one of these very nice Supertex depletion mode Nchannel MOSFETs link to Mouser

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Last edited by Mark Johnson; 20th September 2017 at 01:12 PM. Reason: add Mouser link
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Old 20th September 2017, 03:47 PM   #63
anatech is offline anatech  Canada
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Constant Current Source (CCS) For Audio Applications

Hi Andrew,
Elvee will have notification emails to that effect, so making a post saying you posted somewhere else isn't helpful.

-Chris
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Old 9th February 2018, 09:48 PM   #64
jackinnj is offline jackinnj  United States
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Constant Current Source (CCS) For Audio Applications
I used this setup to measure the current noise of the conventional DMOS cascode current source. The amplifier is the Colin design with noise which ranges 1nV/Rt Hz to a bit lower. The CCS was set for 1mA DC. Frequencies examined 1kHz and 10kHz.

Measured voltage out is 37.2nV/Rt Hz == which if you apply the formula is 3.5pA/RtHz
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Old 9th February 2018, 10:18 PM   #65
john_tracy is offline john_tracy  United States
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The LM334 with the addition of a resistor and diode (resistor is 10X Rset, 1N4148) will give you a zero tempco current source. Cascoding increases performance. The 334 does generate some wide band white noise.
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Old 10th February 2018, 01:05 AM   #66
jackinnj is offline jackinnj  United States
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Constant Current Source (CCS) For Audio Applications
Quote:
Originally Posted by jackinnj View Post
I used this setup to measure the current noise of the conventional DMOS cascode current source. The amplifier is the Colin design with noise which ranges 1nV/Rt Hz to a bit lower. The CCS was set for 1mA DC. Frequencies examined 1kHz and 10kHz.

Measured voltage out is 37.2nV/Rt Hz == which if you apply the formula is 3.5pA/RtHz
I should have mentioned, the switched is closed prior to test. This drains the DC voltage to zero at the preamp input. 10uF is overkill as the f3 is ridiculously low.

The best way to operate is to allow the preamp to settle for 4 or 5 minutes, run a noise test with R4 shorted. S1 closed.

Easier to download the data into Excel than write an AP-Basic Macro!
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Old 10th February 2018, 01:18 AM   #67
Mark Johnson is offline Mark Johnson  United States
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Constant Current Source (CCS) For Audio Applications
Quote:
Originally Posted by john_tracy View Post
The LM334 with the addition of a resistor and diode (resistor is 10X Rset, 1N4148) will give you a zero tempco current source.
What!??!?!

The LM334 datasheet takes great pains to instruct you NOT to use a gold-doped superfast diode like the 1N4148, whose Vfwd and whose tempco dVfwd/dT do not track the (not gold doped) junctions inside the LM334 IC. Instead, the LM334 datasheet tells you to use the (not gold doped) 1N457 diode. Figure below.

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Old 10th February 2018, 01:38 AM   #68
john_tracy is offline john_tracy  United States
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My bad. Poor memory.
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