This circuit clamps current that's above +5.6V and below -5.6V.
Sometimes it is desirable to limit the range of a signal (prevent it from exceeding certain voltage limits) somewhere in a circuit.This circuit will accomplish this. The diode prevents the output from exceeding about +5.6V and -5.6V.
The series resistor limits current during clamping action; however, a side effect is that it adds 10kOhm of series resistance to the signal, so it's a compromise between maintaining a desirable low source resistance and a desirable low clamping current.
On the right half you can observe a complete circuit
On the left side you see a simplified, Thevenin, version of the same board. Feel free to change 66.6Ohm resistor.
Left circuit shows a not stiff voltage divider and poor clamping as the result.
5.6V line on the oscilloscope represents a desired clamping voltage.
