A positive clamper combined with a half wave rectifier creates a positive doubling circuit.
Top left shows the positive clamper which will take the AC signal and DC offset it up on the output to twice the input, e.g., 10 Vpp centered around 0 V at the input becomes 10 Vpp centered around 10 V at the output, i.e., 0 to 20 Vp.
The half wave rectifying circuit to the right has the input source set with a +10 Vdc offset to simulate the output of the positive clamper. The AC signal is rectified creating a DC voltage from the 20 Vp output of the clamper, i.e., 20 Vp from the clamper becomes 20 Vdc at the output of the rectifier.
The large circuit at the bottom shows what happens when you combine the positive clamper with the half wave rectifier and then stack them. It is drawn this way to make it easy to understand and also because most textbooks draw them in a very confusing and unintuitive manner.
