nsakan
Junior Member level 2
homemade digital oscilloscope
Gonzakpo asked a question about having higher voltages than maximum ADC input
> The idea is to suply an operational amplifier (OP) between the adc input maximun
> voltage ranges....
> For example between +0.5V and -0.5V.... (maximun input voltage range of my adc is > 1Vpp)
> Also, configure the GAIN of the OP to 1. (A=R2/21)
Please look at the atached png figure area A abd B between 2 and 3
You coud see an easy solution for Your problem, use two clamping diodes, they must be atached to the supply pins of the devices that You have to protect. Also it could be advisable to have some resistance beween X1-1 and diodes, jut in case that ne overvoltage is not spike but constant signal, like in Your case.. Lot of modern opamps have protection diodes inside of them, please reas the datasheet of both opamp that You would like to use and AD converter carefuly. Also be careful not to slow down the AD convereter input with the slow opama. When You are looking for the opama characteristics, note the the bigest frequency at which Your opamp is capable to delivet 1Vpp swing (for exmple the lrgest frequency tht You coud cheeve with OP07 is something between 60kHz - 80kHz, pg. 7 of OP07C Analog evices datasheet fig. TPC17). It is most likely thay Your ADC have the protection diodes inside of it, and the simplest solution is just to add some resistance in front of it. With such meho You cou hve higher voltages than opamap +/- supply voltage applied, the higher voltages would be cutt-off. Try to make some auxulary supply with nice capacitance, not only big but with low ESR and combination og several types of capacitors for Your cllamp diodes that would keep them on +0.5V and -0.5V, but first carefly reed ADC datasheet and find some aplication notes for it.
I might have some time on weekend, so if You would like send me more details about ADC and I will try to tell You something more.
Sincerely Yours,
Nenad Sakan
Gonzakpo asked a question about having higher voltages than maximum ADC input
> The idea is to suply an operational amplifier (OP) between the adc input maximun
> voltage ranges....
> For example between +0.5V and -0.5V.... (maximun input voltage range of my adc is > 1Vpp)
> Also, configure the GAIN of the OP to 1. (A=R2/21)
Please look at the atached png figure area A abd B between 2 and 3
You coud see an easy solution for Your problem, use two clamping diodes, they must be atached to the supply pins of the devices that You have to protect. Also it could be advisable to have some resistance beween X1-1 and diodes, jut in case that ne overvoltage is not spike but constant signal, like in Your case.. Lot of modern opamps have protection diodes inside of them, please reas the datasheet of both opamp that You would like to use and AD converter carefuly. Also be careful not to slow down the AD convereter input with the slow opama. When You are looking for the opama characteristics, note the the bigest frequency at which Your opamp is capable to delivet 1Vpp swing (for exmple the lrgest frequency tht You coud cheeve with OP07 is something between 60kHz - 80kHz, pg. 7 of OP07C Analog evices datasheet fig. TPC17). It is most likely thay Your ADC have the protection diodes inside of it, and the simplest solution is just to add some resistance in front of it. With such meho You cou hve higher voltages than opamap +/- supply voltage applied, the higher voltages would be cutt-off. Try to make some auxulary supply with nice capacitance, not only big but with low ESR and combination og several types of capacitors for Your cllamp diodes that would keep them on +0.5V and -0.5V, but first carefly reed ADC datasheet and find some aplication notes for it.
I might have some time on weekend, so if You would like send me more details about ADC and I will try to tell You something more.
Sincerely Yours,
Nenad Sakan