What is this circuit's function?

What do you think it's supposed to do ?

Graham

Pooh Bear =E5=AF=AB=E9=81=93=EF=BC=9A

I guess that is protection or boot up circuit....

Best regards, Boki.

It doesn't appear to be connected to very much other than power and ground. As such it will do nothing useful.

Graham

remove the 3v batteries and replace with a 3v3 p-p ac signal, see what happens

martin

If Q46 collector connects a LED, does this circuit mean anything?

I am not sure, but saw it.

Best regards, Boki.

sorry, still no idea..

Best regards, Boki.

What are you copying? Knowing this may help.

Rob =E5=AF=AB=E9=81=93=EF=BC=9A

um... I think it is a LED driving circuit. This part I show is power part I think. due to switch is at collector of Q46 ( of course, series LED first, and then to switch )

Boki.

If you imagine Q45's base as the input, this circuit will be a zero-crossing switch, that is if the input is above 0V, Q46 is on, below 0V the output is off. Q45 serves as a level-shifting impedance-raising transistor. Most of us would add a resistor in Q47's collector to limit the Q46 base current, rather than simply depending on Q47's beta and the 900k resistor. We might also add a hysteresis feedback resistor from Q46-C to Q47-B.

Now, as for the purpose of the 300k pullup on Q45's base... As a zero-crossing switch, the input should not go below -0.5 volts, or Q45's collector-base diode will turn on.

Winfield Hill =E5=AF=AB=E9=81=93=EF=BC=9A

Thank you so much for your advice.

Best regards, Boki.