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Solution

The oscilloscope input impedance is represented in the probe schematic by R2 and C2. Both the oscilloscope and cable capacitances are represented by C2. The high impedance probe isolates the measured circuit by adding a large resistor, R1 in this example, in series with the oscilloscope input. R1 forms a resistive voltage divider with the oscilloscope input resistance, R2.here there are Cp and Rp in parallel

The value of Rp is set to 1 MOhm for a X10 probe and 99 MOhm for a X100 probe for an oscilloscope input resistance of 1 MOhm. Capacitor C1 is adjusted so that the RC product, R1C1, equals the product R2C2. This compensates the probe so that it provides the desired attenuation at all frequencies. Therefore, before using any high impedance passive probe, the user should adjust C1 with a 1 kHz square wave, to seek an optimal compensation. A typical X10 probe has an equivalent input impedance consisting of a 1 M resistance in parallel with 20 pF, where the 20 pF are partly due to the series of C1 and C2 and partly to the stray capacitance of the probe tip to ground, Ctip.

Z1=Cp+Rp

Z2=CpRp/cp+Rp

=21megaohm

K = Z2/ Z1 + Z2

10=z2/z1+z2

Z2 = R2 // 1/sCl = R2 1 + sR2Cl  

R1Cc = R2Cl

R1Cc=20 mega ohm

Z=Z1+Z2

K = Z2// Z1 + Z2

10=21/Z1+21

10Z1+210=21

Z1=18 mega ohm

Que 5

At low frequency Rp is nearly 9Mohm

Que 6

At high frequenc Cp is nearly 100PF