A device is disclosed that includes a control circuit and a scope circuit. The control circuit is configured to delay a voltage signal to generate a first control signal. The scope circuit is configured to be operated in one of a first mode and a second mode according to the first control signal. In the first mode, the scope circuit is configured to generate a first current signal indicating amplitudes of the voltage signal, and in the second mode, the scope circuit is configured to stop generating the first current signal.