Thank you for your reply. Do you mean it is a damping resistor?
But most constant current source circuits do not seem to have this resistance, so I am a little confused about its function
I'm sorry my English is poor, and I don't quite understand what [base stopper] means
A base stopper resistor is a series base resistor used to reduce or prevent ringing and/or oscillation.
The term is a colloquialism. You can call it a damping resistor in that it could reduce the Q of the ringing.
The need for such a resistor depends on the parts, construction, and circuit in which the current source is used.
You could breadboard the current source, and see how the base resistor's presence and value affects the output.
The term is a colloquialism. You can call it a damping resistor in that it could reduce the Q of the ringing.
The need for such a resistor depends on the parts, construction, and circuit in which the current source is used.
You could breadboard the current source, and see how the base resistor's presence and value affects the output.
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Thank you for your reply.
I built a circuit with a bread board for testing
Good, post some results here for discussion.
The resistor lead to the transistor base should be short and direct.
The resistor lead to the transistor base should be short and direct.
If the transistors have wide bandwidths, which they will, this is not a low frequency circuit.
A circuit can oscillate at say 100 MHz without an input at that frequency, or even any input at all.
A circuit can oscillate at say 100 MHz without an input at that frequency, or even any input at all.
Q1 and Q2 are connected in a negative feedback loop, which like all NFB loops, might possibly oscillate. Resistor R4 works with the collector-to-base capacitance of Q1 to provide dominant pole (Miller) compensation, which stabilizes the loop and prevents oscillation. Often the feedback loop is perfectly stable even without R4, depending on device choices and bias levels. But designers include R4 anyway, as an inexpensive belt-and-suspenders safety measure.
Follow-up question if the OP permits,
Does it also serve its purpose if it contributes to adjusting output dc offset?
At times when I couldn't make the dc offset set to an almost zero dc, I attached a small resistor at their bases.
Does it also serve its purpose if it contributes to adjusting output dc offset?
At times when I couldn't make the dc offset set to an almost zero dc, I attached a small resistor at their bases.
Base current is not highly thermally stable, so not an ideal method.
Do you mean the bases of output power transistors? Higher values than necessary may also cause more distortion.
Do you mean the bases of output power transistors? Higher values than necessary may also cause more distortion.
Is that resistor necessary in the Precision Constant-Current Sink example of the TI datasheet of TL431? See p.29, Fig. 10-15 here:
https://www.ti.com/lit/ds/symlink/tl431.pdf
https://www.ti.com/lit/ds/symlink/tl431.pdf
