I have a power supply that is damaging devices that I am trying to measure. I hooked up a scope, and see there is a 0.6V spike when the meter becomes ungrounded which is damaging devices. I need to some how filter out that transient. I have designed and simulated a few circuits, simple zener diode with resistor regulator. Also a shunt regulator using a bjt. The problem is that the load resistance isn't in the same range everytime. Some devices are a few ohms, and some are around 150 and then values in between. The circuits I have made I can design to work for lets say 150, but if the load resistance changes to say 2, then the voltage across it is way to low. The devices are biased at 125mV. Anyone have any thoughts suggestions on how I can do this, what type of circuit would work best? Thanks a lot for your help!!

 

Your post is very confusing. I think you want a constant voltage 0.125V power supply capable of driving loads that range from ∞ down to 2Ω. (~100mA)

Is that right?

What voltage are you starting from?

What is the "meter" you are talking about?

Can you post a schematic of your setup?

 

Yes source voltage is .125V, Keithley 2601A source meter, schematic is the power supply in series with a resistor. Resistor values range from 2 - 100's of ohms. Need to filter out that .6V spike that is 5X's larger than what the devices are meant to handle.

 

Yes source voltage is .125V, Keithley 2601A source meter, schematic is the power supply in series with a resistor. Resistor values range from 2 - 100's of ohms. Need to filter out that .6V spike that is 5X's larger than what the devices are meant to handle.

Get rid of that obsolete piece of crap! Seriously, if the dynamic transient response is that bad it should be replaced.

Make sure that you shut the Keithley off before picking up the probes. Do not turn it back on until the probes are in contact with a new test site.

 

Yes if Keithley can't fix the problem then I will be replacing with another power supply. Do they make relays for small voltages like 300mV?

 

Have you tried a simple LC filter?

http://www.pentodepress.com/calculator/LC-ripple-filter.html

What do you mean when you say

there is a 0.6V spike when the meter becomes ungrounded

Why does the meter become ungrounded?