Hi,
I was wondering if somebody could explain to me why the scope input is usually 1MOhm to ground. I understand that this makes a 10:1 divider when using a 9MOhm probe, however what I don't understand is, why the division, why not use a high impedance input (GOhms) and not use any divider at all ?
Thank you for any explanation.
I was wondering if somebody could explain to me why the scope input is usually 1MOhm to ground. I understand that this makes a 10:1 divider when using a 9MOhm probe, however what I don't understand is, why the division, why not use a high impedance input (GOhms) and not use any divider at all ?
Thank you for any explanation.
Also, the BW of the probe is inversely related to the tip impedance. The higher the tip impedance, the longer it takes to charge the inherent capacitance of the tip, so the probe has a lower BW. This is why higher BW probes have a lower impedance, and the really high-impedance probes have impedance values of 25-50K, feeding a scope input with 50Ohms. These, of course, are active, in that they have amplifiers in them.
This is somewhat simplified, but the concepts hold...
Al