Differentiator

[jinanok]

Hi,

i was trying to differentiate a 3Mhz square wave of 15V peak ,,
i used one 10pF ceramic capacitor and one 1K resistor , i m getting the differentiated wave form but the ouput peek is reducing to 1V ,,

how i will get 15V peek differentated wave form ,,, why the voltage peek is reducing ????????/


please help me to solve this problem.................

 

[ericgibbs]

Hi,

i was trying to differentiate a 3Mhz square wave of 15V peak ,,
i used one 10pF ceramic capacitor and one 1K resistor , i m getting the differentiated wave form but the ouput peek is reducing to 1V ,,

how i will get 15V peek differentated wave form ,,, why the voltage peek is reducing ????????/


please help me to solve this problem.................

hi,

What 'resistance' is the output of the 'diff' seeing, ie: the load impedance.?

also whats driving the 'diff'.?

EDIT: how are you measuring the diff output pulse, eg: scope with probe, resistance/cap of probe/scope.?

 

[jinanok]

the differentiator input is comg from a driver is (EL 7182) and output i m conecting to a CRO ,, latter i have to connect this signal to a 2n2222 for switching ...

 

[ericgibbs]

the differentiator input is comg from a driver is (EL 7182) and output i m conecting to a CRO ,, latter i have to connect this signal to a 2n2222 for switching ...

hi,
If the capacitance of the cro and probe are high the diff signal will be attenuated.

Also if using a *10 probe, check the cap trim.!

Are you using a series resistor from the output of the diff to the base of the 2N2222.?


EDIT: simulations indicate the 2N2222 is not fast enough to give a sharp output pulse.

 

[crutschow]

With a 10pF differentiating capacitor, just about any stray circuit capacitance is greater than that and will reduce the signal amplitude accordingly. Even a 10:1 probe will have close to 10pF of capacitance. Try using a larger capacitor.