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prevent circuit from oscillation

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Jony130

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Hi.
Can you hale my prevent this constant current source circuit from oscillation.
Why this circuit even start to oscillate?
Maybe the circuit is bad?
 

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Add a 100pf cap from output to (-) of U1.
Break connection from U2 out to U1 in(-). Now add 10k resistor to get the connection back.

The new RC slows down the error amp U1. It ts too fast and too much gain.
 
Add a 100pf cap from output to (-) of U1.
Break connection from U2 out to U1 in(-). Now add 10k resistor to get the connection back.

The new RC slows down the error amp U1. It ts too fast and too much gain.
THX I try this tomorrow

Here is a much simpler circuit:
View attachment 71281
But I need a circuit with low Rr voltage drop (Vcc = 5V) and with high Vin voltage to set the current (from 0 to 4V).
 
THX I try this tomorrow


But I need a circuit with low Rr voltage drop (Vcc = 5V) and with high Vin voltage to set the current (from 0 to 4V).
If you use an op amp with rail-to-rail I/O, it should work.
If your collector resistor is really 100Ω, and your maximum current is 4V/10Ω=400mA, then you will need a collector supply voltage much higher than 12V.
 
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