Change your signal to be 9V DC. Now what is the voltage across D1? Hopefully you can do that in your head.

ok so now i got that on the cathode i got 9VDC, while at anode i got 8.3V, so -0.7V

 

Change your signal to be 9V DC. Now what is the voltage across D1? Hopefully you can do that in your head.

so if it was 9VDC the diode would be in reverse polarization and it wouldnt work, we are lucky we are applying an AC signal that stays at 9V for a brief period of time, right?

 

The signal, as you have it connected, will force its voltage at the junction of the two diodes. The bases will then be at Vin +0.65V and Vin - 0.65V. In a real circuit , there will be a series resistance in the signal path, so the voltages at the bases will not swing as far as the signal.

can j

Change your signal to be 9V DC. Now what is the voltage across D1? Hopefully you can do that in your head.

can u check if i said correctly?

 

Hello all, can someone tell me if i understood this circuit properly?:

This circuit is basically identical to the last post i did, but with a difference, there is an op amp acting as voltage buffer, what he does here is this:

at pin "+" i connected the sine wave and the pin - is connected to the output.
Now what amplifier gonna do is a comparison beetwen the pin + voltage and pin -, and will try to match its output in order to make pin - voltage as close as possible to pin +, in this way with the op amp we compensate the drop of bjt internal diodes etc, cus we use our input as reference.

Secondly we got a low impedance as output.

Is this correct? for what other reason this circuit is used?

 

so if it was 9VDC the diode would be in reverse polarization and it wouldnt work, we are lucky we are applying an AC signal that stays at 9V for a brief period of time, right?

You did not answer my question. And no, the diode is not reverse biased.

That amplifier should never be given a signal of more than about ±8V if you want it to work correctly.

I think you are over-thinking this and confusing yourself. I have no idea what you are getting at with the second sentence.

 

You did not answer my question. And no, the diode is not reverse biased.

That amplifier should never be given a signal of more than about ±8V if you want it to work correctly.

I think you are over-thinking this and confusing yourself. I have no idea what you are getting at with the second sentence.

-0.7V in case of 9V so it wont work

Yeah probably overthinking, no idea and thats the main issue

 

Basically the diodes are forward conducting during the complete AC cycle until/if saturation occurs at the peaks of the AC waveform.