Every now and then I come upon a situation where I want a complementary version of the TL431 or TLV431. I was setting up SOA limit protection for an amp and I found myself wishing for one. Then I realized how they are designed inside, and it's not that hard.
This is a circuit that maintains its reference with respect to the cathode, unlike the TL431, which maintains its reference with respect to the anode. Then it pushes current out the anode instead of pulling it into the cathode.
I haven't simulated it, but it looks like it should work. If you try it and it doesn't work, let me know.
This is a circuit that maintains its reference with respect to the cathode, unlike the TL431, which maintains its reference with respect to the anode. Then it pushes current out the anode instead of pulling it into the cathode.
I haven't simulated it, but it looks like it should work. If you try it and it doesn't work, let me know.
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I have used the TL431 as a negative shunt regulator as well. It worked. It only becomes more tricky when you want to buffer it with a more powerful transistor.
With this circuit, it's the same as buffering a TL431 on the positive rail. This is the PNP version of the TL431, if that helps.
An LM10 could also work here, but the reference voltage is 0.2V, so the resistors have to change.
I see some flaws to the circuit originally shown. Details will be worked out later.
I see some flaws to the circuit originally shown. Details will be worked out later.
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