[Why diode voltage is 0.7V?]

Hello, all

Just a question (I have not found an answer for this elsewhere...):

The voltage of a silicon diode is 0.7V. This depends on many factors, including the geometry of the PN junction. My question is: there is a certain range of acceptable values for that geometry. Why the geometry that gives that 0.7V was chosen?

Tiago

[Oscilloscope overshooting in RC high-pass filter]

Hello, all

This is my first message to the forum. I am need of some assistance in the following problem.

I have mounted an RC high pass circuit, where R = 100K and C = 100nF (hence, cutoff frequency is around 15.5Hz). When I feed the circuit with a 1 Hz square wave with 0V offset and 2V peak-to-peak, the output (voltage in the resistor) should be +-1V in the edges of the square waves followed by an exponential decay to zero, right?

The oscilloscope, however, is reading a maximum voltage value of +-2V - hence, a 1V overshoot. All configurations are correct, such as probe gain, input bandwidth limitation, etc (it is possible to see both waveforms - input and output - on the screen)

My hypothesis for this are:
- The high spike is due to the high voltage variation (this should not make sense, since there is a resistor in series with the capacitor)
- The oscilloscope - a digital one - has sampling dificulties to find sudden high frequency spots while in a large time scale
- My questioning is wrong and the results are correct

What is the correct answer?

Thanks
Tiago