How does this current source work?

Thread Starter

sp2821

Joined Jan 8, 2014
23
Hi,

I was reading an application note from ADI (AN-968) about current sources and saw a circuit below.
The note only had basic description of the circuit and I'm wondering how the circuit works (especially D1, D2, Q1 and Q2)
Why are there 2 diodes and how do R2 and R3 help preventing thermal runaway?

Thank you!

upload_2017-7-24_17-19-19.png
 

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dl324

Joined Mar 30, 2015
16,846
The diodes bias the transistors so they're always on.

The app note describes how R2, R3, and the sense resistor prevent thermal runaway.
 
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