Hello! I have square-wave signal from the generator, but it is unipolar, i.e. GND to +15V. In my application I need some negative DC bias, but there is one and the main problem - fast pulse response needed with 50-100 nanoseconds rise and fall times, so this circuit must be at least high-speed. See the attachment. Thanks...

 

Why not capacitively couple it, so it goes both ways. You could bring the negitive side to whatever voltage using diodes.

 

Could you draw schematics of it?

 

Greetings Santon,

Here is a link to the section in AAC ebook on diode clamping. The technique Bill mentioned is referred to as dc-restoration. It involves introducing a capacitor into the signal line to block the existing DC component of the signal and then using a diode and a voltage reference to establish the new DC component needed.

hgmjr

 

Thanks for good info!
As I understood, capacitor coupling is suitable for sine wave signals, but what will be with the square-wave signal?

 

The low freq parts are attenuated more than the high freq parts. If the cap is big enough, you can't tell the difference, otherwise the edges get through pretty cleanly.