Tool/software:
Hi Sir,
I want to design current source as below for LM4041. This schematic from LM4041 datasheet.
1) May i use the MMBT3906(package SOT23) to replace 2N2905 and 2N3964?
2) Is there other suggest part nuber small SMD package transistor for this apllication?
Hi Sir,
For my apllication. I modify schematic as bleow. Colud you hlep to double check this application is fine?
1) +15V change to +12V
2) 2N2905 and 2N3964 change to MMBT3906*2
Hi Sir,
If i use LM4051-ADJ to this schematic. The typical reference voltage is 1.212V.
I want to know the 1.24V how to get it? or i need to modify the formula as below?
Iout=1.212/R1
Hi Sir,
The voltage of formula don't need to fixed to 1.24V right? Because the formula is fixed volatge 1.24V on the datashee.
Hi Sir,
The voltage of formula don't need to fixed to 1.24V right? Because the formula is fixed volatge 1.24V on the datashee.
When i use the schematic as below, the formula need to change to Iout=1.212V/R1 ?
The following parameter are come from datasheet.
Hi Sir,
I have other question need to check with you.
Below is normal schematic.
When i remove the R5, there is 0.62253V on VM2 (BJT VEC) and 11.38V on VM3
. May i know where are these voltage come from?
Hi Sir,
Got it.
Other question need to check with you.
If i modify the paramter below. I can get same current as before schematic.
1) May i know any side effect for this change?
2) May i know what is current source limit range for this modify? (?uA~?mA)
Modify parameter:
input voltage=5V
Rs= 24KΩ
Hi Ian,
The maximum current of the LM4041 is the constraint to maintain:
Thanks,
Joshua
Hi Joshua,
1)This forward current is on LM4051 maximum current right?
1) I want to know why the current source limit range as bleow on datasheet? (1uA~100mA)
3) If i modify the paramter below. I can get same current as before schematic.
1) May i know any side effect for this change?
2) May i know what is current source limit range for this modify? (?uA~?mA)
Modify parameter:
input voltage=5V
Rs= 24KΩ
Hi Joshua,
You have made is that that 208uA min will flow through the IC guaranteeing a proper minimum operating current, there should be no negative side effects.
1) The current of 208uA -> 5V/24KΩ=208uA
2) I calculate the current through LM4051 on TINA, the current is 98.12uA.
May i know which one is the correct current?
Hi Joshua,
I will use this circuit for current soruce and seirial one resistor(R2) for INA228 detect volatge on R2 as below.
1) Does it fine to this desing?
Current source= 1.2xxV/68R ≈ 17mA
Vin=5V
2) When i increase R2(>170R) to some value, the current will start to drop as below. May i know the root cause for this drop?
