A Interesting new programmable constant current source
LT3092
http://www.linear.com/pc/productDet...3092&utm_medium=email&utm_campaign=LT_Insider
LT3092
http://www.linear.com/pc/productDet...3092&utm_medium=email&utm_campaign=LT_Insider
Hi!
It is alright, if it is affordable = budget price
And the crucial question from me is of course:
How good quality
and how clean
is this Costant current source?
And from this follows a second question:
What does this offer, that we can not achieve with 1 ordinary N-JFET ??
Or one JFET + one MOSFET tansistor to provide even much more current than 200mA ??
So, what do I gain, in the end, from buying that one, instead of do it myself.
wonders
lineup
It is alright, if it is affordable = budget price
And the crucial question from me is of course:
How good quality
and how clean
is this Costant current source?
And from this follows a second question:
What does this offer, that we can not achieve with 1 ordinary N-JFET ??
Or one JFET + one MOSFET tansistor to provide even much more current than 200mA ??
So, what do I gain, in the end, from buying that one, instead of do it myself.
wonders
lineup
Regarding the output noise
Linear claims the following for
Reference Current RMS Output Noise = 1nA RMS
The also have the following appnote on noise reduction
When a reduction in the noise of the current source is
desired, a small capacitor can be placed across RSET (CSET
in Figure 7). Normally, the 10μA reference current source
generates noise current levels of 2.7pA/√Hz (0.7nARMS
over the 10Hz to 100kHz bandwidth). The SET pin resistor
generates a spot noise equal to in = √4kT/R (k = Boltzmann’s
constant, 1.38 • 10–23J/°K, and T is absolute temperature)
which is RMS-summed with the noise generated by the
10μA reference current source. Placing a CSET capacitor
across RSET (as shown in Figure 7) bypasses this noise
current. Note that this noise reduction capacitor increases
start-up time as a factor of the time constant formed by
RSET • CSET
The idea of using a LM317 is very sound indeed, one could also use a small voltage reference chip but connected in a similar way we used it as a CCS for ICP sensors.
Later with the emergence of ICP microphones this trick still worked rather well having enough bandwidth and low enough noise.
Linear claims the following for
Reference Current RMS Output Noise = 1nA RMS
The also have the following appnote on noise reduction
When a reduction in the noise of the current source is
desired, a small capacitor can be placed across RSET (CSET
in Figure 7). Normally, the 10μA reference current source
generates noise current levels of 2.7pA/√Hz (0.7nARMS
over the 10Hz to 100kHz bandwidth). The SET pin resistor
generates a spot noise equal to in = √4kT/R (k = Boltzmann’s
constant, 1.38 • 10–23J/°K, and T is absolute temperature)
which is RMS-summed with the noise generated by the
10μA reference current source. Placing a CSET capacitor
across RSET (as shown in Figure 7) bypasses this noise
current. Note that this noise reduction capacitor increases
start-up time as a factor of the time constant formed by
RSET • CSET
The idea of using a LM317 is very sound indeed, one could also use a small voltage reference chip but connected in a similar way we used it as a CCS for ICP sensors.
Later with the emergence of ICP microphones this trick still worked rather well having enough bandwidth and low enough noise.
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