High Speed Peak Detector

What is the input voltage range, and the minimum length of the peak?

What output signal do you need? I suspect you want a comparator. What is the actual problem you're trying to solve?

Thank you for your respond Mr. Ladisch.

I will start with your last question. We are performing electrostatic discharge test (IEC 61000-4-2) in our company and we need an external device(other than oscilloscope) to do proficiency testing.Secondly, Esd voltages range between 1 kV to 10 kV and I am planning to use voltage divider and peak detector circuit with opams. In conclusion, my purpose is detect and measure the peak voltage. Which opamp would you recommend me to measure such fast signals? Do you have another idea for measuring the peak voltage?

You could look at the peak voltage detector from below link.

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/167314/super-high-speed-peak-detector-needed

Esd voltage waveform:

Hi Behtan,

your request is rather unusual. The height of ESD pulse coming out of an ESD pistol is very well known, because you can easily measure the DC voltage of this high voltage from which the ESD pulse is generated by simply closing a switching contact.

And the other end of ESD testing, where the ESD pulse is applied to, is usually examined by the help of a fast oscilloscope. No one would want to use a peak detector as peak detection is way too complex in this frequency range of interest. Remember that serious ESD testing deals with sub-picosecond rise times. That would really be a hard job for a peak detector circuit.

Another issue is the voltage dividing. You cannot simply divide down an ESD pulse of sub-picosecond rise time, because you would need a frequency compensated voltage divider of up to 10GHz and above. Only the design of such a voltage divider would be a true master task. That's why very high frequency oscilloscopes costs their money.

Kai

Hi Kai,

Thank you for your respond.

You're right there are easier ways to measure the peak voltage. However, as I said before we need external device because we want to perform inter-laboratory measurement comparisons with this device. For this reason, I would really appreciate it if you could give me another advice.

Hi Behtan,

I have discussed fast peak detectors in the following threads:

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/986057/opa615-figure-48-in-datasheet-results-not-as-expected/3673810?tisearch=e2e-sitesearch&keymatch=larry%20AND%20kai#3673810

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/940064/how-to-improve-the-accuracy-of-peak-detector-as-high-as-posssible/3473673?tisearch=e2e-sitesearch&keymatch=yatao%20AND%20kai#3473673

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/718099/opa860-opa860-sample-hold-circuit

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/730231/opa615-high-speed-peak-detector-for-burst-signal

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/737331/opa615-fast-pulse-positive-detector-using-opa615

Kai

Hi Kai,

It turns out esd voltage peak detector is more challenging than I've imagined . Thus I decided to make a peak detector for surge voltage regarding that it is much more slower than esd voltage. I read the threads which you've sent me however I could not decide which one to use. For instance, I think opa615 figure 48 would be sufficent for my voltage waveform yet someone mentioned that circuit is a bit problematic.

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Could you suggest component and circuit diagram for me?

I attached the voltage waveform below.

Regards,

Behtan Umut Mercan

Rise time is approximately 1.2 microseconds.

Sorry I sent to wrong waveform.The one I wanted to measure is attached.

Hi Behtan,

I would do it this way:

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/940064/how-to-improve-the-accuracy-of-peak-detector-as-high-as-posssible/3473673#3473673

The OPA615 and OPA860, on the other hand, are extremely fast but not very precise.

Kai

Hello again Kai,

I'm very grateful to you for all your help. 

I have another question. 

I constantly charge my capacitor and I am guessing overcharging the capacitor will affect it performance(or damage it). Do I have to discharge it? How can I know when to discharge it?

My second question is I have designed my circuit with BAT81 but I think Philips do not produce it now.Could you suggest me another component? I think BAT81S will work but I am not sure.

I have attached my circuit below.

Regards,

Behtan Umut Mercan

Hi Bethan,

a peak detector is no integrator. Because of this you cannot overcharge the capacitor of a peak detector.

The BAT17 is a perfect choice. But keep the input signal below 4V.

To discharge the cap just put a resistor in parallel to C1 and R3:

You could also use the less expensive OPA356, eventually.

Kai

Hi Kai,

If I understand correctly I can use capacitor for peak detector without discharging.

About BAT17 I tried to use it however it did not work properly without 1MEG ohm resistor. I attached to simulation file. I'll try to find schottky diode with higher breakdown voltage. (You've already helped me a lot)

bat17.TSC

Hi Behtan,

I don't see any issue:

behtan_ths4631.TSC

But I see that your file doesn't work properly. Seems to be an error of TINA-TI. This happens sometimes. Close TINA-TI and open it again. If this doesn't help, draw the layout from scratch again in a new file and dismiss the erroneous file.

Kai

Hi Kai,

I guess my circuit does not work properly because I didn't use  1 MEG ohm resistor. Because when I use the 1 MEG ohm resistor for 2 and 3 V input voltage, it couldn't hold the peak voltage.

Hi Behtan,

display the voltage drop across SD2 and you will see that the reverse voltage exceeds 4V.

You cannot have both, ultra fast reaction time of Schottky diode and high maximum reverse voltage. So either you reduce the input voltage range and can use the BAT17 or similar ultra fast Schottky diode or you desire high input voltage signals with high reverse voltage, then you need to choose a slower Schottky diode with higher reverse breakdown voltage. It's your decision

Kai