Hi,
I just need Low Drop Out Regulator. Is your simple circuit LDO? alec_t is saying that his little complicated circuit has ~0.1V drop out.
Hello Willen and Alex,
I designed that simple circuit based on your specifications, therefore it works the way you said it should work. It works from at least 9.5v down to 6.0v and always provides an output of 5.0 volts.
Your stated specs do not require a 0.1v drop out voltage max, it requires a 1.0v drop out voltage max.
You stated:
1. 9v down to 6v
2. 5v output
3. 10ma output
The circuit i provided does that. If you have other specs to add then you'll have to consider what might change.
I might add that Alex's circuit is not a bad circuit so if you wish to provide two transistors you can get longer battery life.
So the choice is yours, to go with a very simple circuit which would draw more current from the battery, or go with a more complex circuit that will allow a 9v battery to run the transmitter for a longer time period. If it was mine, i would add the two transistors, or else use a switching regulator. I hate wasting battery energy
If you do add the two transistors check for oscillations at the output with various conditions of load just in case that circuit needs compensation.
Also, change R1 from 1.5k to 700 Ohms or close to that value.
Also, if you see any oscillation you can try placing a small value capacitor across R4, such as 0.001uf. That should help to compensate, but be aware these kinds of regulators are sometimes hard to compensate so lets hope we get lucky
Oh yeah, one small problem with your circuit Alex. The resistor R1 is not of sufficient size to allow the TL431 to work with it's specified minimum cathode current of 1ma. Decreasing this to around 700 ohms should solve this problem without upsetting anything else.