Overvoltage/Overload clipping detector

[s.b.f]

I was trying to design a kind of clip detector circuit which can detect either current or voltage clipping. This clipping detector is required for a differential driver circuit, which can drive up to 2App current @8Vpp. The supply is 12V and the circuit is band limited to 70MHz. However, the input signal never exceeds 20MHz.
first, we tried to attenuate output voltage and compare it with input signal to see if there is any inconsistency with input and output signal (this difference was accepted within a predefined range). The problem with this structure was that the gain of driver is varying with load and frequency and its not feasible to do this by a predefined gain/attenuator stage.

I was wondering if there is an alternative way to detect voltage/current clipping. I would appreciate it if anybody could help me in this regard.

Thanks
S.B.F

 

[barry]

Interesting problem. I think you might also have to worry about phase shift if you are trying to compare input to output.

But, here's a thought. If your circuit can put out a maximum of, say, 10Volts, have a circuit that detects when the output reaches 10 volts. Anything below 10 volts is not clipped, right?

 

[expert_vision]

What do you intend to do when clipping is detected ?
Just measure Vpp and App and when it gets close to your max range (get's close to clipping), do whatever you have to do (change gain, attenuate, ...).

 

[chuckey]

You could try to see if the DC conditions are changing in the output amplifier when it starts to clip and use this as an indicator. Most amplifiers run into non linearity before they start to clip.
Frank