The input section

The input amplifiers are a bit more complex. The input is AC coupled with U1, which has very high input impedance. AC coupling means that the DC component (offset) from any input signal will be removed. The gain of the first amplifier is R2/R1, or 1 in this case.

Oscilloscope probes come in times-one or times-ten varieties. In fact, some have an X1/X10 selector switch, as shown in the following diagram:

Oscilloscope input amplifiers

A times-ten oscilloscope probe multiplies the input impedance of your scope by a factor of 10. So your 1-megohm input scope now has an input impedance of 10 megohm. However, since nothing in life is free, it also reduces the signal level by a factor of 10. So, if it is not corrected, a 1-volt signal will appear as a 0.1-volt signal on your scope. Many modern scopes do this automatically. Ours has a switch instead.

The reason modern oscilloscopes have this option is that a 10-megaohm probe will tend to load a high impedance less than a 1 megohm probe...